diff --git a/include/config/overworld.h b/include/config/overworld.h
index 5a6cb1e955..5b774ec558 100644
--- a/include/config/overworld.h
+++ b/include/config/overworld.h
@@ -55,8 +55,10 @@
 #define OW_MON_WANDER_WALK             TRUE       // If true, OW pokemon with MOVEMENT_TYPE_WANDER will walk-in-place in between steps.
 // Follower Pokémon
 #define OW_FOLLOWERS_ENABLED           FALSE      // Enables follower Pokémon, HGSS style. Requires OW_POKEMON_OBJECT_EVENTS. Note that additional scripting may be required for them to be fully supported!
-#define OW_FOLLOWERS_BOBBING           TRUE       // If true, follower pokemon will bob up and down during their idle & walking animations
-#define OW_FOLLOWERS_POKEBALLS         TRUE       // Followers will emerge from the pokeball they are stored in, instead of a normal pokeball
+#define OW_FOLLOWERS_BOBBING           TRUE       // If TRUE, follower Pokémon will bob up and down during their idle & walking animations
+#define OW_FOLLOWERS_POKEBALLS         TRUE       // If TRUE, follower Pokémon will emerge from the Poké Ball they are stored in, instead of a normal Poké Ball
+#define OW_FOLLOWERS_WEATHER_FORMS     FALSE      // If TRUE, Castform and Cherrim gain FORM_CHANGE_OVERWORLD_WEATHER, which will make them transform in the overworld based on the weather.
+#define OW_FOLLOWERS_COPY_WILD_PKMN    FALSE      // If TRUE, follower Pokémon that know Transform or have Illusion/Imposter will copy wild Pokémon at random.
 
 // Out-of-battle Ability effects
 #define OW_SYNCHRONIZE_NATURE       GEN_LATEST // In Gen8+, if a Pokémon with Synchronize leads the party, wild Pokémon will always have their same Nature as opposed to the 50% chance in previous games. Gift Pokémon excluded.
diff --git a/include/constants/form_change_types.h b/include/constants/form_change_types.h
index 8af9740cad..8cf2e37e1b 100644
--- a/include/constants/form_change_types.h
+++ b/include/constants/form_change_types.h
@@ -144,4 +144,11 @@
 // param2: ability to check, optional
 #define FORM_CHANGE_BATTLE_BEFORE_MOVE_CATEGORY 25
 
+// Form change that activates when overworld weather changes.
+// param1: weather to check.
+#define FORM_CHANGE_OVERWORLD_WEATHER           26
+
+// Form change that activates when the Pokémon is deposited into the PC or Daycare.
+#define FORM_CHANGE_DEPOSIT                     27
+
 #endif // GUARD_CONSTANTS_FORM_CHANGE_TYPES_H
diff --git a/include/event_object_movement.h b/include/event_object_movement.h
index f6aa18280f..ce30769f17 100644
--- a/include/event_object_movement.h
+++ b/include/event_object_movement.h
@@ -148,6 +148,7 @@ void ClearObjectEventMovement(struct ObjectEvent *objectEvent, struct Sprite *sp
 void ObjectEventClearHeldMovement(struct ObjectEvent *);
 void ObjectEventClearHeldMovementIfActive(struct ObjectEvent *);
 struct Pokemon *GetFirstLiveMon(void);
+u16 GetOverworldWeatherSpecies(u16 species);
 void UpdateFollowingPokemon(void);
 void RemoveFollowingPokemon(void);
 struct ObjectEvent *GetFollowerObject(void);
diff --git a/src/battle_util.c b/src/battle_util.c
index fc916a76c4..d9b742d023 100644
--- a/src/battle_util.c
+++ b/src/battle_util.c
@@ -10925,21 +10925,18 @@ bool32 DoesSpeciesUseHoldItemToChangeForm(u16 species, u16 heldItemId)
     u32 i;
     const struct FormChange *formChanges = GetSpeciesFormChanges(species);
 
-    if (formChanges != NULL)
+    for (i = 0; formChanges != NULL && formChanges[i].method != FORM_CHANGE_TERMINATOR; i++)
     {
-        for (i = 0; formChanges[i].method != FORM_CHANGE_TERMINATOR; i++)
+        switch (formChanges[i].method)
         {
-            switch (formChanges[i].method)
-            {
-            case FORM_CHANGE_BATTLE_MEGA_EVOLUTION_ITEM:
-            case FORM_CHANGE_BATTLE_PRIMAL_REVERSION:
-            case FORM_CHANGE_BATTLE_ULTRA_BURST:
-            case FORM_CHANGE_ITEM_HOLD:
-            case FORM_CHANGE_BEGIN_BATTLE:
-                if (formChanges[i].param1 == heldItemId)
-                    return TRUE;
-                break;
-            }
+        case FORM_CHANGE_BATTLE_MEGA_EVOLUTION_ITEM:
+        case FORM_CHANGE_BATTLE_PRIMAL_REVERSION:
+        case FORM_CHANGE_BATTLE_ULTRA_BURST:
+        case FORM_CHANGE_ITEM_HOLD:
+        case FORM_CHANGE_BEGIN_BATTLE:
+            if (formChanges[i].param1 == heldItemId)
+                return TRUE;
+            break;
         }
     }
     return FALSE;
@@ -11070,103 +11067,98 @@ u16 GetBattleFormChangeTargetSpecies(u32 battler, u16 method)
     u32 targetSpecies = species;
     const struct FormChange *formChanges = GetSpeciesFormChanges(species);
     struct Pokemon *mon = &GetBattlerParty(battler)[gBattlerPartyIndexes[battler]];
-    u16 heldItem;
+    u16 heldItem = gBattleMons[battler].item;
 
-    if (formChanges != NULL)
+    for (i = 0; formChanges != NULL && formChanges[i].method != FORM_CHANGE_TERMINATOR; i++)
     {
-        heldItem = gBattleMons[battler].item;
-
-        for (i = 0; formChanges[i].method != FORM_CHANGE_TERMINATOR; i++)
+        if (method == formChanges[i].method && species != formChanges[i].targetSpecies)
         {
-            if (method == formChanges[i].method && species != formChanges[i].targetSpecies)
+            switch (method)
             {
-                switch (method)
+            case FORM_CHANGE_BATTLE_MEGA_EVOLUTION_ITEM:
+            case FORM_CHANGE_BATTLE_PRIMAL_REVERSION:
+            case FORM_CHANGE_BATTLE_ULTRA_BURST:
+                if (heldItem == formChanges[i].param1)
+                    targetSpecies = formChanges[i].targetSpecies;
+                break;
+            case FORM_CHANGE_BATTLE_MEGA_EVOLUTION_MOVE:
+                if (gBattleMons[battler].moves[0] == formChanges[i].param1
+                    || gBattleMons[battler].moves[1] == formChanges[i].param1
+                    || gBattleMons[battler].moves[2] == formChanges[i].param1
+                    || gBattleMons[battler].moves[3] == formChanges[i].param1)
+                    targetSpecies = formChanges[i].targetSpecies;
+                break;
+            case FORM_CHANGE_BATTLE_SWITCH:
+                if (formChanges[i].param1 == GetBattlerAbility(battler) || formChanges[i].param1 == ABILITY_NONE)
+                    targetSpecies = formChanges[i].targetSpecies;
+                break;
+            case FORM_CHANGE_BATTLE_HP_PERCENT:
+                if (formChanges[i].param1 == GetBattlerAbility(battler))
                 {
-                case FORM_CHANGE_BATTLE_MEGA_EVOLUTION_ITEM:
-                case FORM_CHANGE_BATTLE_PRIMAL_REVERSION:
-                case FORM_CHANGE_BATTLE_ULTRA_BURST:
-                    if (heldItem == formChanges[i].param1)
-                        targetSpecies = formChanges[i].targetSpecies;
-                    break;
-                case FORM_CHANGE_BATTLE_MEGA_EVOLUTION_MOVE:
-                    if (gBattleMons[battler].moves[0] == formChanges[i].param1
-                     || gBattleMons[battler].moves[1] == formChanges[i].param1
-                     || gBattleMons[battler].moves[2] == formChanges[i].param1
-                     || gBattleMons[battler].moves[3] == formChanges[i].param1)
-                        targetSpecies = formChanges[i].targetSpecies;
-                    break;
-                case FORM_CHANGE_BATTLE_SWITCH:
-                    if (formChanges[i].param1 == GetBattlerAbility(battler) || formChanges[i].param1 == ABILITY_NONE)
-                        targetSpecies = formChanges[i].targetSpecies;
-                    break;
-                case FORM_CHANGE_BATTLE_HP_PERCENT:
-                    if (formChanges[i].param1 == GetBattlerAbility(battler))
+                    // We multiply by 100 to make sure that integer division doesn't mess with the health check.
+                    u32 hpCheck = gBattleMons[battler].hp * 100 * 100 / gBattleMons[battler].maxHP;
+                    switch(formChanges[i].param2)
                     {
-                        // We multiply by 100 to make sure that integer division doesn't mess with the health check.
-                        u32 hpCheck = gBattleMons[battler].hp * 100 * 100 / gBattleMons[battler].maxHP;
-                        switch(formChanges[i].param2)
-                        {
-                        case HP_HIGHER_THAN:
-                            if (hpCheck > formChanges[i].param3 * 100)
-                                targetSpecies = formChanges[i].targetSpecies;
-                            break;
-                        case HP_LOWER_EQ_THAN:
-                            if (hpCheck <= formChanges[i].param3 * 100)
-                                targetSpecies = formChanges[i].targetSpecies;
-                            break;
-                        }
+                    case HP_HIGHER_THAN:
+                        if (hpCheck > formChanges[i].param3 * 100)
+                            targetSpecies = formChanges[i].targetSpecies;
+                        break;
+                    case HP_LOWER_EQ_THAN:
+                        if (hpCheck <= formChanges[i].param3 * 100)
+                            targetSpecies = formChanges[i].targetSpecies;
+                        break;
                     }
-                    break;
-                case FORM_CHANGE_BATTLE_GIGANTAMAX:
-                    if (GetMonData(mon, MON_DATA_GIGANTAMAX_FACTOR))
-                        targetSpecies = formChanges[i].targetSpecies;
-                    break;
-                case FORM_CHANGE_BATTLE_WEATHER:
-                    // Check if there is a required ability and if the battler's ability does not match it
-                    // or is suppressed. If so, revert to the no weather form.
-                    if (formChanges[i].param2
-                        && GetBattlerAbility(battler) != formChanges[i].param2
-                        && formChanges[i].param1 == B_WEATHER_NONE)
-                    {
-                        targetSpecies = formChanges[i].targetSpecies;
-                    }
-                    // We need to revert the weather form if the field is under Air Lock, too.
-                    else if (!WEATHER_HAS_EFFECT && formChanges[i].param1 == B_WEATHER_NONE)
-                    {
-                        targetSpecies = formChanges[i].targetSpecies;
-                    }
-                    // Otherwise, just check for a match between the weather and the form change table.
-                    // Added a check for whether the weather is in effect to prevent end-of-turn soft locks with Cloud Nine / Air Lock
-                    else if (((gBattleWeather & formChanges[i].param1) && WEATHER_HAS_EFFECT)
-                        || (gBattleWeather == B_WEATHER_NONE && formChanges[i].param1 == B_WEATHER_NONE))
-                    {
-                        targetSpecies = formChanges[i].targetSpecies;
-                    }
-                    break;
-                case FORM_CHANGE_BATTLE_TURN_END:
-                case FORM_CHANGE_HIT_BY_MOVE:
-                    if (formChanges[i].param1 == GetBattlerAbility(battler))
-                        targetSpecies = formChanges[i].targetSpecies;
-                    break;
-                case FORM_CHANGE_STATUS:
-                    if (gBattleMons[battler].status1 & formChanges[i].param1)
-                        targetSpecies = formChanges[i].targetSpecies;
-                    break;
-                case FORM_CHANGE_BATTLE_TERASTALLIZATION:
-                    if (GetBattlerTeraType(battler) == formChanges[i].param1)
-                        targetSpecies = formChanges[i].targetSpecies;
-                    break;
-                case FORM_CHANGE_BATTLE_BEFORE_MOVE:
-                    if (formChanges[i].param1 == gCurrentMove
-                     && (formChanges[i].param2 == ABILITY_NONE || formChanges[i].param2 == GetBattlerAbility(battler)))
-                        targetSpecies = formChanges[i].targetSpecies;
-                    break;
-                case FORM_CHANGE_BATTLE_BEFORE_MOVE_CATEGORY:
-                    if (formChanges[i].param1 == GetBattleMoveCategory(gCurrentMove)
-                     && (formChanges[i].param2 == ABILITY_NONE || formChanges[i].param2 == GetBattlerAbility(battler)))
-                        targetSpecies = formChanges[i].targetSpecies;
-                    break;
                 }
+                break;
+            case FORM_CHANGE_BATTLE_GIGANTAMAX:
+                if (GetMonData(mon, MON_DATA_GIGANTAMAX_FACTOR))
+                    targetSpecies = formChanges[i].targetSpecies;
+                break;
+            case FORM_CHANGE_BATTLE_WEATHER:
+                // Check if there is a required ability and if the battler's ability does not match it
+                // or is suppressed. If so, revert to the no weather form.
+                if (formChanges[i].param2
+                    && GetBattlerAbility(battler) != formChanges[i].param2
+                    && formChanges[i].param1 == B_WEATHER_NONE)
+                {
+                    targetSpecies = formChanges[i].targetSpecies;
+                }
+                // We need to revert the weather form if the field is under Air Lock, too.
+                else if (!WEATHER_HAS_EFFECT && formChanges[i].param1 == B_WEATHER_NONE)
+                {
+                    targetSpecies = formChanges[i].targetSpecies;
+                }
+                // Otherwise, just check for a match between the weather and the form change table.
+                // Added a check for whether the weather is in effect to prevent end-of-turn soft locks with Cloud Nine / Air Lock
+                else if (((gBattleWeather & formChanges[i].param1) && WEATHER_HAS_EFFECT)
+                    || (gBattleWeather == B_WEATHER_NONE && formChanges[i].param1 == B_WEATHER_NONE))
+                {
+                    targetSpecies = formChanges[i].targetSpecies;
+                }
+                break;
+            case FORM_CHANGE_BATTLE_TURN_END:
+            case FORM_CHANGE_HIT_BY_MOVE:
+                if (formChanges[i].param1 == GetBattlerAbility(battler))
+                    targetSpecies = formChanges[i].targetSpecies;
+                break;
+            case FORM_CHANGE_STATUS:
+                if (gBattleMons[battler].status1 & formChanges[i].param1)
+                    targetSpecies = formChanges[i].targetSpecies;
+                break;
+            case FORM_CHANGE_BATTLE_TERASTALLIZATION:
+                if (GetBattlerTeraType(battler) == formChanges[i].param1)
+                    targetSpecies = formChanges[i].targetSpecies;
+                break;
+            case FORM_CHANGE_BATTLE_BEFORE_MOVE:
+                if (formChanges[i].param1 == gCurrentMove
+                    && (formChanges[i].param2 == ABILITY_NONE || formChanges[i].param2 == GetBattlerAbility(battler)))
+                    targetSpecies = formChanges[i].targetSpecies;
+                break;
+            case FORM_CHANGE_BATTLE_BEFORE_MOVE_CATEGORY:
+                if (formChanges[i].param1 == GetBattleMoveCategory(gCurrentMove)
+                    && (formChanges[i].param2 == ABILITY_NONE || formChanges[i].param2 == GetBattlerAbility(battler)))
+                    targetSpecies = formChanges[i].targetSpecies;
+                break;
             }
         }
     }
diff --git a/src/data/pokemon/form_change_tables.h b/src/data/pokemon/form_change_tables.h
index 340bdb1fa6..1cab4fc833 100644
--- a/src/data/pokemon/form_change_tables.h
+++ b/src/data/pokemon/form_change_tables.h
@@ -410,22 +410,33 @@ static const struct FormChange sGlalieFormChangeTable[] = {
 
 #if P_FAMILY_CASTFORM
 static const struct FormChange sCastformFormChangeTable[] = {
+#if OW_FOLLOWERS_WEATHER_FORMS == TRUE
+    {FORM_CHANGE_OVERWORLD_WEATHER, SPECIES_CASTFORM_SUNNY,  WEATHER_SUNNY_CLOUDS},
+    {FORM_CHANGE_OVERWORLD_WEATHER, SPECIES_CASTFORM_SUNNY,  WEATHER_DROUGHT},
+    {FORM_CHANGE_OVERWORLD_WEATHER, SPECIES_CASTFORM_RAINY,  WEATHER_RAIN},
+    {FORM_CHANGE_OVERWORLD_WEATHER, SPECIES_CASTFORM_RAINY,  WEATHER_RAIN_THUNDERSTORM},
+    {FORM_CHANGE_OVERWORLD_WEATHER, SPECIES_CASTFORM_RAINY,  WEATHER_DOWNPOUR},
+    {FORM_CHANGE_OVERWORLD_WEATHER, SPECIES_CASTFORM_SNOWY,  WEATHER_SNOW},
+    {FORM_CHANGE_OVERWORLD_WEATHER, SPECIES_CASTFORM_NORMAL, WEATHER_NONE},
+    {FORM_CHANGE_BEGIN_BATTLE,      SPECIES_CASTFORM_NORMAL}, // To prevent Battles from being affected.
+    {FORM_CHANGE_DEPOSIT,           SPECIES_CASTFORM_NORMAL}, // To prevent depositing weather forms into the PC.
+#endif //OW_FOLLOWERS_WEATHER_FORMS
 #if B_WEATHER_FORMS >= GEN_5
-    {FORM_CHANGE_BATTLE_WEATHER,                SPECIES_CASTFORM_SUNNY, B_WEATHER_SUN, ABILITY_FORECAST},
-    {FORM_CHANGE_BATTLE_WEATHER,                SPECIES_CASTFORM_RAINY, B_WEATHER_RAIN, ABILITY_FORECAST},
-    {FORM_CHANGE_BATTLE_WEATHER,                SPECIES_CASTFORM_SNOWY, B_WEATHER_HAIL | B_WEATHER_SNOW, ABILITY_FORECAST},
-    {FORM_CHANGE_BATTLE_WEATHER,                SPECIES_CASTFORM_NORMAL, ~(B_WEATHER_SUN | B_WEATHER_RAIN | B_WEATHER_HAIL | B_WEATHER_SNOW), ABILITY_FORECAST},
-    {FORM_CHANGE_BATTLE_WEATHER,                SPECIES_CASTFORM_NORMAL, B_WEATHER_NONE, ABILITY_FORECAST},
+    {FORM_CHANGE_BATTLE_WEATHER,    SPECIES_CASTFORM_SUNNY, B_WEATHER_SUN, ABILITY_FORECAST},
+    {FORM_CHANGE_BATTLE_WEATHER,    SPECIES_CASTFORM_RAINY, B_WEATHER_RAIN, ABILITY_FORECAST},
+    {FORM_CHANGE_BATTLE_WEATHER,    SPECIES_CASTFORM_SNOWY, B_WEATHER_HAIL | B_WEATHER_SNOW, ABILITY_FORECAST},
+    {FORM_CHANGE_BATTLE_WEATHER,    SPECIES_CASTFORM_NORMAL, ~(B_WEATHER_SUN | B_WEATHER_RAIN | B_WEATHER_HAIL | B_WEATHER_SNOW), ABILITY_FORECAST},
+    {FORM_CHANGE_BATTLE_WEATHER,    SPECIES_CASTFORM_NORMAL, B_WEATHER_NONE, ABILITY_FORECAST},
 #else
-    {FORM_CHANGE_BATTLE_WEATHER,                SPECIES_CASTFORM_SUNNY, B_WEATHER_SUN},
-    {FORM_CHANGE_BATTLE_WEATHER,                SPECIES_CASTFORM_RAINY, B_WEATHER_RAIN},
-    {FORM_CHANGE_BATTLE_WEATHER,                SPECIES_CASTFORM_SNOWY, B_WEATHER_HAIL | B_WEATHER_SNOW},
-    {FORM_CHANGE_BATTLE_WEATHER,                SPECIES_CASTFORM_NORMAL, ~(B_WEATHER_SUN | B_WEATHER_RAIN | B_WEATHER_HAIL | B_WEATHER_SNOW)},
-    {FORM_CHANGE_BATTLE_WEATHER,                SPECIES_CASTFORM_NORMAL, B_WEATHER_NONE},
+    {FORM_CHANGE_BATTLE_WEATHER,    SPECIES_CASTFORM_SUNNY, B_WEATHER_SUN},
+    {FORM_CHANGE_BATTLE_WEATHER,    SPECIES_CASTFORM_RAINY, B_WEATHER_RAIN},
+    {FORM_CHANGE_BATTLE_WEATHER,    SPECIES_CASTFORM_SNOWY, B_WEATHER_HAIL | B_WEATHER_SNOW},
+    {FORM_CHANGE_BATTLE_WEATHER,    SPECIES_CASTFORM_NORMAL, ~(B_WEATHER_SUN | B_WEATHER_RAIN | B_WEATHER_HAIL | B_WEATHER_SNOW)},
+    {FORM_CHANGE_BATTLE_WEATHER,    SPECIES_CASTFORM_NORMAL, B_WEATHER_NONE},
 #endif
-    {FORM_CHANGE_BATTLE_SWITCH,                 SPECIES_CASTFORM_NORMAL},
-    {FORM_CHANGE_FAINT,                         SPECIES_CASTFORM_NORMAL},
-    {FORM_CHANGE_END_BATTLE,                    SPECIES_CASTFORM_NORMAL},
+    {FORM_CHANGE_BATTLE_SWITCH,     SPECIES_CASTFORM_NORMAL},
+    {FORM_CHANGE_FAINT,             SPECIES_CASTFORM_NORMAL},
+    {FORM_CHANGE_END_BATTLE,        SPECIES_CASTFORM_NORMAL},
     {FORM_CHANGE_TERMINATOR},
 };
 #endif //P_FAMILY_CASTFORM
@@ -531,18 +542,24 @@ static const struct FormChange sBurmyFormChangeTable[] = {
 
 #if P_FAMILY_CHERUBI
 static const struct FormChange sCherrimFormChangeTable[] = {
+#if OW_FOLLOWERS_WEATHER_FORMS == TRUE
+    {FORM_CHANGE_OVERWORLD_WEATHER, SPECIES_CHERRIM_SUNSHINE, WEATHER_DROUGHT},
+    {FORM_CHANGE_OVERWORLD_WEATHER, SPECIES_CHERRIM_OVERCAST, WEATHER_NONE},
+    {FORM_CHANGE_BEGIN_BATTLE,      SPECIES_CHERRIM_OVERCAST}, // To prevent Battles from being affected.
+    {FORM_CHANGE_DEPOSIT,           SPECIES_CHERRIM_OVERCAST}, // To prevent depositing weather forms into the PC.
+#endif //OW_FOLLOWERS_WEATHER_FORMS
 #if B_WEATHER_FORMS >= GEN_5
-    {FORM_CHANGE_BATTLE_WEATHER,                SPECIES_CHERRIM_SUNSHINE, B_WEATHER_SUN, ABILITY_FLOWER_GIFT},
-    {FORM_CHANGE_BATTLE_WEATHER,                SPECIES_CHERRIM_OVERCAST, ~B_WEATHER_SUN, ABILITY_FLOWER_GIFT},
-    {FORM_CHANGE_BATTLE_WEATHER,                SPECIES_CHERRIM_OVERCAST, B_WEATHER_NONE, ABILITY_FLOWER_GIFT},
+    {FORM_CHANGE_BATTLE_WEATHER,    SPECIES_CHERRIM_SUNSHINE, B_WEATHER_SUN, ABILITY_FLOWER_GIFT},
+    {FORM_CHANGE_BATTLE_WEATHER,    SPECIES_CHERRIM_OVERCAST, ~B_WEATHER_SUN, ABILITY_FLOWER_GIFT},
+    {FORM_CHANGE_BATTLE_WEATHER,    SPECIES_CHERRIM_OVERCAST, B_WEATHER_NONE, ABILITY_FLOWER_GIFT},
 #else
-    {FORM_CHANGE_BATTLE_WEATHER,                SPECIES_CHERRIM_SUNSHINE, B_WEATHER_SUN},
-    {FORM_CHANGE_BATTLE_WEATHER,                SPECIES_CHERRIM_OVERCAST, ~B_WEATHER_SUN},
-    {FORM_CHANGE_BATTLE_WEATHER,                SPECIES_CHERRIM_OVERCAST, B_WEATHER_NONE},
+    {FORM_CHANGE_BATTLE_WEATHER,    SPECIES_CHERRIM_SUNSHINE, B_WEATHER_SUN},
+    {FORM_CHANGE_BATTLE_WEATHER,    SPECIES_CHERRIM_OVERCAST, ~B_WEATHER_SUN},
+    {FORM_CHANGE_BATTLE_WEATHER,    SPECIES_CHERRIM_OVERCAST, B_WEATHER_NONE},
 #endif
-    {FORM_CHANGE_BATTLE_SWITCH,                 SPECIES_CHERRIM_OVERCAST},
-    {FORM_CHANGE_FAINT,                         SPECIES_CHERRIM_OVERCAST},
-    {FORM_CHANGE_END_BATTLE,                    SPECIES_CHERRIM_OVERCAST},
+    {FORM_CHANGE_BATTLE_SWITCH,     SPECIES_CHERRIM_OVERCAST},
+    {FORM_CHANGE_FAINT,             SPECIES_CHERRIM_OVERCAST},
+    {FORM_CHANGE_END_BATTLE,        SPECIES_CHERRIM_OVERCAST},
     {FORM_CHANGE_TERMINATOR},
 };
 #endif //P_FAMILY_CHERUBI
diff --git a/src/daycare.c b/src/daycare.c
index 26b86ec1e2..6b6b84ac58 100644
--- a/src/daycare.c
+++ b/src/daycare.c
@@ -259,6 +259,13 @@ static void StorePokemonInDaycare(struct Pokemon *mon, struct DaycareMon *daycar
         TakeMailFromMon(mon);
     }
 
+    u32 newSpecies = GetFormChangeTargetSpecies(mon, FORM_CHANGE_DEPOSIT, 0);
+    if (newSpecies != GetMonData(mon, MON_DATA_SPECIES))
+    {
+        SetMonData(mon, MON_DATA_SPECIES, &newSpecies);
+        CalculateMonStats(mon);
+    }
+
     daycareMon->mon = mon->box;
     daycareMon->steps = 0;
     ZeroMonData(mon);
diff --git a/src/event_object_movement.c b/src/event_object_movement.c
index 581cd94620..80423aa316 100644
--- a/src/event_object_movement.c
+++ b/src/event_object_movement.c
@@ -25,6 +25,7 @@
 #include "metatile_behavior.h"
 #include "overworld.h"
 #include "palette.h"
+#include "party_menu.h"
 #include "pokemon.h"
 #include "pokeball.h"
 #include "random.h"
@@ -2154,21 +2155,24 @@ static void RefreshFollowerGraphics(struct ObjectEvent *objEvent)
     }
 }
 
-static u16 GetOverworldCastformSpecies(void)
+u16 GetOverworldWeatherSpecies(u16 species)
 {
-    switch (GetCurrentWeather())
+    u32 i;
+    u32 weather = GetCurrentWeather();
+    const struct FormChange *formChanges = GetSpeciesFormChanges(species);
+
+    for (i = 0; formChanges != NULL && formChanges[i].method != FORM_CHANGE_TERMINATOR; i++)
     {
-    case WEATHER_SUNNY_CLOUDS:
-    case WEATHER_DROUGHT:
-        return SPECIES_CASTFORM_SUNNY;
-    case WEATHER_RAIN:
-    case WEATHER_RAIN_THUNDERSTORM:
-    case WEATHER_DOWNPOUR:
-        return SPECIES_CASTFORM_RAINY;
-    case WEATHER_SNOW:
-        return SPECIES_CASTFORM_SNOWY;
+        // Unlike other form change checks, we don't do the "species != formChanges[i].targetSpecies" check
+        if (formChanges[i].method == FORM_CHANGE_OVERWORLD_WEATHER)
+        {
+            if (formChanges[i].param1 == weather)
+                return formChanges[i].targetSpecies;
+            else if (formChanges[i].param1 == WEATHER_NONE) // Set the default form for weather not defined in form change table
+                species = formChanges[i].targetSpecies;
+        }
     }
-    return SPECIES_CASTFORM_NORMAL;
+    return species;
 }
 
 static bool8 GetMonInfo(struct Pokemon *mon, u16 *species, u8 *form, u8 *shiny)
@@ -2189,8 +2193,8 @@ static bool8 GetMonInfo(struct Pokemon *mon, u16 *species, u8 *form, u8 *shiny)
     case SPECIES_UNOWN:
         *form = GET_UNOWN_LETTER(mon->box.personality);
         break;
-    case SPECIES_CASTFORM: // form is based on overworld weather
-        *species = GetOverworldCastformSpecies();
+    default:
+        *species = GetOverworldWeatherSpecies(*species);
         break;
     }
     return TRUE;
@@ -5337,14 +5341,20 @@ static bool32 EndFollowerTransformEffect(struct ObjectEvent *objectEvent, struct
 static bool32 TryStartFollowerTransformEffect(struct ObjectEvent *objectEvent, struct Sprite *sprite)
 {
     u32 multi;
-    if (GET_BASE_SPECIES_ID(OW_SPECIES(objectEvent)) == SPECIES_CASTFORM
-        && OW_SPECIES(objectEvent) != (multi = GetOverworldCastformSpecies()))
+    struct Pokemon *mon;
+    u32 ability;
+    if (DoesSpeciesHaveFormChangeMethod(OW_SPECIES(objectEvent), FORM_CHANGE_OVERWORLD_WEATHER)
+        && OW_SPECIES(objectEvent) != (multi = GetOverworldWeatherSpecies(OW_SPECIES(objectEvent))))
     {
         sprite->data[7] = TRANSFORM_TYPE_WEATHER << 8;
+        PlaySE(SE_M_MINIMIZE);
         return TRUE;
     }
-    else if ((Random() & 0xFFFF) < 18 && GetLocalWildMon(FALSE)
-            && (OW_SPECIES(objectEvent) == SPECIES_MEW || OW_SPECIES(objectEvent) == SPECIES_DITTO))
+
+    if (OW_FOLLOWERS_COPY_WILD_PKMN
+        && (MonKnowsMove(mon = GetFirstLiveMon(), MOVE_TRANSFORM)
+         || (ability = GetMonAbility(mon)) == ABILITY_IMPOSTER || ability == ABILITY_ILLUSION)
+        && (Random() & 0xFFFF) < 18 && GetLocalWildMon(FALSE))
     {
         sprite->data[7] = TRANSFORM_TYPE_RANDOM_WILD << 8;
         PlaySE(SE_M_MINIMIZE);
@@ -5378,7 +5388,7 @@ static bool8 UpdateFollowerTransformEffect(struct ObjectEvent *objectEvent, stru
             break;
         case TRANSFORM_TYPE_WEATHER:
             multi = objectEvent->graphicsId;
-            objectEvent->graphicsId = GetOverworldCastformSpecies();
+            objectEvent->graphicsId = GetOverworldWeatherSpecies(OW_SPECIES(objectEvent));
             if (!objectEvent->graphicsId)
             {
                 objectEvent->graphicsId = multi;
diff --git a/src/field_weather.c b/src/field_weather.c
index 7d3c4caf4f..ae69289d8a 100644
--- a/src/field_weather.c
+++ b/src/field_weather.c
@@ -246,11 +246,28 @@ void SetNextWeather(u8 weather)
     gWeatherPtr->finishStep = 0;
 }
 
+static void UpdateWeatherForms(void)
+{
+    s32 i;
+    for (i = 0; i < PARTY_SIZE; i++)
+    {
+        struct Pokemon *mon = &gPlayerParty[i];
+        u16 species = GetMonData(mon, MON_DATA_SPECIES);
+        u16 targetSpecies = GetOverworldWeatherSpecies(species);
+        if (species != targetSpecies)
+        {
+            SetMonData(mon, MON_DATA_SPECIES, &targetSpecies);
+            CalculateMonStats(mon);
+        }
+    }
+}
+
 void SetCurrentAndNextWeather(u8 weather)
 {
     PlayRainStoppingSoundEffect();
     gWeatherPtr->currWeather = weather;
     gWeatherPtr->nextWeather = weather;
+    UpdateWeatherForms();
 }
 
 void SetCurrentAndNextWeatherNoDelay(u8 weather)
@@ -260,6 +277,7 @@ void SetCurrentAndNextWeatherNoDelay(u8 weather)
     gWeatherPtr->nextWeather = weather;
     // Overrides the normal delay during screen fading.
     gWeatherPtr->readyForInit = TRUE;
+    UpdateWeatherForms();
 }
 
 static void Task_WeatherInit(u8 taskId)
@@ -287,6 +305,7 @@ static void Task_WeatherMain(u8 taskId)
             gWeatherPtr->palProcessingState = WEATHER_PAL_STATE_CHANGING_WEATHER;
             gWeatherPtr->currWeather = gWeatherPtr->nextWeather;
             gWeatherPtr->weatherChangeComplete = TRUE;
+            UpdateWeatherForms();
         }
     }
     else
diff --git a/src/pokemon.c b/src/pokemon.c
index efb4d91abb..fcbde3ba4a 100644
--- a/src/pokemon.c
+++ b/src/pokemon.c
@@ -4425,7 +4425,7 @@ u32 GetGMaxTargetSpecies(u32 species)
 {
     const struct FormChange *formChanges = GetSpeciesFormChanges(species);
     u32 i;
-    for (i = 0; formChanges[i].method != FORM_CHANGE_TERMINATOR; i++)
+    for (i = 0; formChanges != NULL && formChanges[i].method != FORM_CHANGE_TERMINATOR; i++)
     {
         if (formChanges[i].method == FORM_CHANGE_BATTLE_GIGANTAMAX)
             return formChanges[i].targetSpecies;
@@ -6588,6 +6588,7 @@ u32 GetFormChangeTargetSpeciesBoxMon(struct BoxPokemon *boxMon, u16 method, u32
                         targetSpecies = formChanges[i].targetSpecies;
                     break;
                 case FORM_CHANGE_WITHDRAW:
+                case FORM_CHANGE_DEPOSIT:
                 case FORM_CHANGE_FAINT:
                 case FORM_CHANGE_DAYS_PASSED:
                     targetSpecies = formChanges[i].targetSpecies;
@@ -6623,7 +6624,7 @@ void TrySetDayLimitToFormChange(struct Pokemon *mon)
     u16 species = GetMonData(mon, MON_DATA_SPECIES, NULL);
     const struct FormChange *formChanges = GetSpeciesFormChanges(species);
 
-    for (i = 0; formChanges[i].method != FORM_CHANGE_TERMINATOR; i++)
+    for (i = 0; formChanges != NULL && formChanges[i].method != FORM_CHANGE_TERMINATOR; i++)
     {
         if (formChanges[i].method == FORM_CHANGE_DAYS_PASSED && species != formChanges[i].targetSpecies)
         {
@@ -6638,13 +6639,10 @@ bool32 DoesSpeciesHaveFormChangeMethod(u16 species, u16 method)
     u32 i;
     const struct FormChange *formChanges = GetSpeciesFormChanges(species);
 
-    if (formChanges != NULL)
+    for (i = 0; formChanges != NULL && formChanges[i].method != FORM_CHANGE_TERMINATOR; i++)
     {
-        for (i = 0; formChanges[i].method != FORM_CHANGE_TERMINATOR; i++)
-        {
-            if (method == formChanges[i].method && species != formChanges[i].targetSpecies)
-                return TRUE;
-        }
+        if (method == formChanges[i].method && species != formChanges[i].targetSpecies)
+            return TRUE;
     }
 
     return FALSE;
diff --git a/src/pokemon_storage_system.c b/src/pokemon_storage_system.c
index 81dff0f435..9714293931 100644
--- a/src/pokemon_storage_system.c
+++ b/src/pokemon_storage_system.c
@@ -550,6 +550,7 @@ EWRAM_DATA static u8 sMovingMonOrigBoxId = 0;
 EWRAM_DATA static u8 sMovingMonOrigBoxPos = 0;
 EWRAM_DATA static bool8 sAutoActionOn = 0;
 EWRAM_DATA static bool8 sJustOpenedBag = 0;
+EWRAM_DATA static bool8 sRefreshDisplayMonGfx = FALSE;
 
 // Main tasks
 static void Task_InitPokeStorage(u8);
@@ -844,7 +845,7 @@ static void TilemapUtil_DrawPrev(u8);
 static void TilemapUtil_Draw(u8);
 
 // Form changing
-void SetMonFormPSS(struct BoxPokemon *boxMon);
+void SetMonFormPSS(struct BoxPokemon *boxMon, u32 method);
 void UpdateSpeciesSpritePSS(struct BoxPokemon *boxmon);
 
 static const u8 gText_JustOnePkmn[] = _("There is just one POKéMON with you.");
@@ -3773,12 +3774,14 @@ static void GiveChosenBagItem(void)
         {
             struct Pokemon *mon = &gPlayerParty[pos];
             SetMonData(&gPlayerParty[pos], MON_DATA_HELD_ITEM, &itemId);
-            SetMonFormPSS(&mon->box);
+            SetMonFormPSS(&mon->box, FORM_CHANGE_ITEM_HOLD);
+            UpdateSpeciesSpritePSS(&mon->box);
         }
         else
         {
             SetCurrentBoxMonData(pos, MON_DATA_HELD_ITEM, &itemId);
-            SetMonFormPSS(&gPokemonStoragePtr->boxes[StorageGetCurrentBox()][pos]);
+            SetMonFormPSS(&gPokemonStoragePtr->boxes[StorageGetCurrentBox()][pos], FORM_CHANGE_ITEM_HOLD);
+            UpdateSpeciesSpritePSS(&gPokemonStoragePtr->boxes[StorageGetCurrentBox()][pos]);
         }
 
         RemoveBagItem(itemId, 1);
@@ -6346,11 +6349,14 @@ static void PlaceMon(void)
     case CURSOR_AREA_IN_PARTY:
         SetPlacedMonData(TOTAL_BOXES_COUNT, sCursorPosition);
         SetPlacedMonSprite(TOTAL_BOXES_COUNT, sCursorPosition);
+        struct Pokemon *mon = &gPlayerParty[sCursorPosition];
+        UpdateSpeciesSpritePSS(&mon->box);
         break;
     case CURSOR_AREA_IN_BOX:
         boxId = StorageGetCurrentBox();
         SetPlacedMonData(boxId, sCursorPosition);
         SetPlacedMonSprite(boxId, sCursorPosition);
+        UpdateSpeciesSpritePSS(&gPokemonStoragePtr->boxes[boxId][sCursorPosition]);
         break;
     default:
         return;
@@ -6390,12 +6396,15 @@ static void SetPlacedMonData(u8 boxId, u8 position)
     if (boxId == TOTAL_BOXES_COUNT)
     {
         gPlayerParty[position] = sStorage->movingMon;
-        if (&gPlayerParty[position] == GetFirstLiveMon())
+        struct Pokemon *mon = &gPlayerParty[position];
+        if (mon == GetFirstLiveMon())
             gFollowerSteps = 0;
+        SetMonFormPSS(&mon->box, FORM_CHANGE_WITHDRAW);
     }
     else
     {
         SetBoxMonAt(boxId, position, &sStorage->movingMon.box);
+        SetMonFormPSS(&gPokemonStoragePtr->boxes[boxId][position], FORM_CHANGE_DEPOSIT);
     }
 }
 
@@ -6900,13 +6909,13 @@ static void ReshowDisplayMon(void)
         TryRefreshDisplayMon();
 }
 
-void SetMonFormPSS(struct BoxPokemon *boxMon)
+void SetMonFormPSS(struct BoxPokemon *boxMon, u32 method)
 {
-    u16 targetSpecies = GetFormChangeTargetSpeciesBoxMon(boxMon, FORM_CHANGE_ITEM_HOLD, 0);
+    u16 targetSpecies = GetFormChangeTargetSpeciesBoxMon(boxMon, method, 0);
     if (targetSpecies != GetBoxMonData(boxMon, MON_DATA_SPECIES, NULL))
     {
         SetBoxMonData(boxMon, MON_DATA_SPECIES, &targetSpecies);
-        UpdateSpeciesSpritePSS(boxMon);
+        sRefreshDisplayMonGfx = TRUE;
     }
 }
 
@@ -8885,14 +8894,16 @@ static void TakeItemFromMon(u8 cursorArea, u8 cursorPos)
     {
         SetCurrentBoxMonData(cursorPos, MON_DATA_HELD_ITEM, &itemId);
         SetBoxMonIconObjMode(cursorPos, ST_OAM_OBJ_BLEND);
-        SetMonFormPSS(&gPokemonStoragePtr->boxes[StorageGetCurrentBox()][cursorPos]);
+        SetMonFormPSS(&gPokemonStoragePtr->boxes[StorageGetCurrentBox()][cursorPos], FORM_CHANGE_ITEM_HOLD);
+        UpdateSpeciesSpritePSS(&gPokemonStoragePtr->boxes[StorageGetCurrentBox()][cursorPos]);
     }
     else
     {
         struct Pokemon *mon = &gPlayerParty[cursorPos];
         SetMonData(&gPlayerParty[cursorPos], MON_DATA_HELD_ITEM, &itemId);
         SetPartyMonIconObjMode(cursorPos, ST_OAM_OBJ_BLEND);
-        SetMonFormPSS(&mon->box);
+        SetMonFormPSS(&mon->box, FORM_CHANGE_ITEM_HOLD);
+        UpdateSpeciesSpritePSS(&mon->box);
     }
 
     sStorage->movingItemId = sStorage->displayMonItemId;
@@ -8927,7 +8938,8 @@ static void SwapItemsWithMon(u8 cursorArea, u8 cursorPos)
         itemId = GetCurrentBoxMonData(cursorPos, MON_DATA_HELD_ITEM);
         SetCurrentBoxMonData(cursorPos, MON_DATA_HELD_ITEM, &sStorage->movingItemId);
         sStorage->movingItemId = itemId;
-        SetMonFormPSS(&gPokemonStoragePtr->boxes[StorageGetCurrentBox()][cursorPos]);
+        SetMonFormPSS(&gPokemonStoragePtr->boxes[StorageGetCurrentBox()][cursorPos], FORM_CHANGE_ITEM_HOLD);
+        UpdateSpeciesSpritePSS(&gPokemonStoragePtr->boxes[StorageGetCurrentBox()][cursorPos]);
     }
     else
     {
@@ -8935,7 +8947,8 @@ static void SwapItemsWithMon(u8 cursorArea, u8 cursorPos)
         itemId = GetMonData(&gPlayerParty[cursorPos], MON_DATA_HELD_ITEM);
         SetMonData(&gPlayerParty[cursorPos], MON_DATA_HELD_ITEM, &sStorage->movingItemId);
         sStorage->movingItemId = itemId;
-        SetMonFormPSS(&mon->box);
+        SetMonFormPSS(&mon->box, FORM_CHANGE_ITEM_HOLD);
+        UpdateSpeciesSpritePSS(&mon->box);
     }
 
     id = GetItemIconIdxByPosition(CURSOR_AREA_IN_HAND, 0);
@@ -8957,14 +8970,16 @@ static void GiveItemToMon(u8 cursorArea, u8 cursorPos)
     {
         SetCurrentBoxMonData(cursorPos, MON_DATA_HELD_ITEM, &sStorage->movingItemId);
         SetBoxMonIconObjMode(cursorPos, ST_OAM_OBJ_NORMAL);
-        SetMonFormPSS(&gPokemonStoragePtr->boxes[StorageGetCurrentBox()][cursorPos]);
+        SetMonFormPSS(&gPokemonStoragePtr->boxes[StorageGetCurrentBox()][cursorPos], FORM_CHANGE_ITEM_HOLD);
+        UpdateSpeciesSpritePSS(&gPokemonStoragePtr->boxes[StorageGetCurrentBox()][cursorPos]);
     }
     else
     {
         struct Pokemon *mon = &gPlayerParty[cursorPos];
         SetMonData(&gPlayerParty[cursorPos], MON_DATA_HELD_ITEM, &sStorage->movingItemId);
         SetPartyMonIconObjMode(cursorPos, ST_OAM_OBJ_NORMAL);
-        SetMonFormPSS(&mon->box);
+        SetMonFormPSS(&mon->box, FORM_CHANGE_ITEM_HOLD);
+        UpdateSpeciesSpritePSS(&mon->box);
     }
 }
 
@@ -8984,14 +8999,16 @@ static void MoveItemFromMonToBag(u8 cursorArea, u8 cursorPos)
     {
         SetCurrentBoxMonData(cursorPos, MON_DATA_HELD_ITEM, &itemId);
         SetBoxMonIconObjMode(cursorPos, ST_OAM_OBJ_BLEND);
-        SetMonFormPSS(&gPokemonStoragePtr->boxes[StorageGetCurrentBox()][cursorPos]);
+        SetMonFormPSS(&gPokemonStoragePtr->boxes[StorageGetCurrentBox()][cursorPos], FORM_CHANGE_ITEM_HOLD);
+        UpdateSpeciesSpritePSS(&gPokemonStoragePtr->boxes[StorageGetCurrentBox()][cursorPos]);
     }
     else
     {
         struct Pokemon *mon = &gPlayerParty[cursorPos];
         SetMonData(&gPlayerParty[cursorPos], MON_DATA_HELD_ITEM, &itemId);
         SetPartyMonIconObjMode(cursorPos, ST_OAM_OBJ_BLEND);
-        SetMonFormPSS(&mon->box);
+        SetMonFormPSS(&mon->box, FORM_CHANGE_ITEM_HOLD);
+        UpdateSpeciesSpritePSS(&mon->box);
     }
 }
 
@@ -10051,8 +10068,12 @@ void UpdateSpeciesSpritePSS(struct BoxPokemon *boxMon)
     sStorage->displayMonPalette = GetMonSpritePalFromSpeciesAndPersonality(species, isShiny, pid);
     if (!sJustOpenedBag)
     {
-        LoadDisplayMonGfx(species, pid);
-        StartDisplayMonMosaicEffect();
+        if (sRefreshDisplayMonGfx)
+        {
+            LoadDisplayMonGfx(species, pid);
+            StartDisplayMonMosaicEffect();
+            sRefreshDisplayMonGfx = FALSE;
+        }
 
         // Recreate icon sprite
         if (sInPartyMenu)
@@ -10062,9 +10083,10 @@ void UpdateSpeciesSpritePSS(struct BoxPokemon *boxMon)
         }
         else
         {
-            DestroyBoxMonIcon(sStorage->boxMonsSprites[sCursorPosition]);
+            DestroyBoxMonIconAtPosition(sCursorPosition);
             CreateBoxMonIconAtPos(sCursorPosition);
-            SetBoxMonIconObjMode(sCursorPosition, GetBoxMonData(boxMon, MON_DATA_HELD_ITEM) == ITEM_NONE);
+            if (sStorage->boxOption == OPTION_MOVE_ITEMS)
+                SetBoxMonIconObjMode(sCursorPosition, (GetBoxMonData(boxMon, MON_DATA_HELD_ITEM) == ITEM_NONE ? ST_OAM_OBJ_NORMAL : ST_OAM_OBJ_BLEND));
         }
     }
     sJustOpenedBag = FALSE;