diff --git a/include/party_menu.h b/include/party_menu.h
index 75fe7b958..23a17d753 100644
--- a/include/party_menu.h
+++ b/include/party_menu.h
@@ -55,6 +55,7 @@ void ItemUseCB_PPUp(u8 taskId, TaskFunc task);
 u16 ItemIdToBattleMoveId(u16 item);
 bool8 IsMoveHm(u16 move);
 bool8 MonKnowsMove(struct Pokemon *mon, u16 move);
+bool8 BoxMonKnowsMove(struct BoxPokemon *mon, u16 move);
 void ItemUseCB_TMHM(u8 taskId, TaskFunc task);
 void ItemUseCB_RareCandy(u8 taskId, TaskFunc task);
 void ItemUseCB_SacredAsh(u8 taskId, TaskFunc task);
diff --git a/include/pokemon.h b/include/pokemon.h
index 6a13f7432..e55e2e7ec 100644
--- a/include/pokemon.h
+++ b/include/pokemon.h
@@ -439,4 +439,5 @@ u8 *sub_806F4F8(u8 id, u8 arg1);
 u16 GetFormSpeciesId(u16 speciesId, u8 formId);
 u8 GetFormIdFromFormSpeciesId(u16 formSpeciesId);
 u16 GetFormChangeTargetSpecies(struct Pokemon *mon, u16 method, u32 arg);
+u16 GetFormChangeTargetSpeciesBoxMon(struct BoxPokemon *mon, u16 method, u32 arg);
 #endif // GUARD_POKEMON_H
diff --git a/src/party_menu.c b/src/party_menu.c
index d471a92a8..86e443f76 100755
--- a/src/party_menu.c
+++ b/src/party_menu.c
@@ -4640,6 +4640,18 @@ bool8 MonKnowsMove(struct Pokemon *mon, u16 move)
     return FALSE;
 }
 
+bool8 BoxMonKnowsMove(struct BoxPokemon *mon, u16 move)
+{
+    u8 i;
+
+    for (i = 0; i < MAX_MON_MOVES; i++)
+    {
+        if (GetMonData(mon, MON_DATA_MOVE1 + i) == move)
+            return TRUE;
+    }
+    return FALSE;
+}
+
 static void DisplayLearnMoveMessage(const u8 *str)
 {
     StringExpandPlaceholders(gStringVar4, str);
diff --git a/src/pokemon.c b/src/pokemon.c
index bc04c42f9..021eca1d1 100644
--- a/src/pokemon.c
+++ b/src/pokemon.c
@@ -8049,12 +8049,17 @@ u8 GetFormIdFromFormSpeciesId(u16 formSpeciesId)
     return targetFormId;
 }
 
-// returns SPECIES_NONE if no form change is possible
 u16 GetFormChangeTargetSpecies(struct Pokemon *mon, u16 method, u32 arg) 
+{
+    return GetFormChangeTargetSpeciesBoxMon(&mon->box, method, arg);
+}
+
+// returns SPECIES_NONE if no form change is possible
+u16 GetFormChangeTargetSpeciesBoxMon(struct BoxPokemon *mon, u16 method, u32 arg) 
 {
     u32 i;
     u16 targetSpecies = SPECIES_NONE;
-    u16 originalSpecies = GetMonData(mon, MON_DATA_SPECIES, NULL);
+    u16 originalSpecies = GetBoxMonData(mon, MON_DATA_SPECIES, NULL);
     const struct FormChange *formChanges = gFormChangeTablePointers[originalSpecies];
 
     if (formChanges == NULL)
@@ -8064,11 +8069,11 @@ u16 GetFormChangeTargetSpecies(struct Pokemon *mon, u16 method, u32 arg)
     {
         if (method == formChanges[i].method)
         {
-            u32 ability = GetAbilityBySpecies(originalSpecies, GetMonData(mon, MON_DATA_ABILITY_NUM, NULL));
+            u32 ability = GetAbilityBySpecies(originalSpecies, GetBoxMonData(mon, MON_DATA_ABILITY_NUM, NULL));
             switch (method)
             {
             case FORM_ITEM_HOLD:
-                if (GetMonData(mon, MON_DATA_HELD_ITEM, NULL) == formChanges[i].param1 && (ability == formChanges[i].param2 || formChanges[i].param2 == ABILITY_NONE))
+                if (GetBoxMonData(mon, MON_DATA_HELD_ITEM, NULL) == formChanges[i].param1 && (ability == formChanges[i].param2 || formChanges[i].param2 == ABILITY_NONE))
                     targetSpecies = formChanges[i].targetSpecies;
                 break;
             case FORM_ITEM_USE: 
@@ -8076,7 +8081,7 @@ u16 GetFormChangeTargetSpecies(struct Pokemon *mon, u16 method, u32 arg)
                     targetSpecies = formChanges[i].targetSpecies;
                 break;
             case FORM_MOVE:
-                if (MonKnowsMove(mon, formChanges[i].param1) != formChanges[i].param2)
+                if (BoxMonKnowsMove(mon, formChanges[i].param1) != formChanges[i].param2)
                     targetSpecies = formChanges[i].targetSpecies;
                 break;
             case FORM_ITEM_USE_DAY:
diff --git a/src/pokemon_storage_system.c b/src/pokemon_storage_system.c
index 92f45cb28..9029fa425 100644
--- a/src/pokemon_storage_system.c
+++ b/src/pokemon_storage_system.c
@@ -870,6 +870,10 @@ static void UnkUtil_Run(void);
 static void UnkUtil_CpuRun(struct UnkUtilData *);
 static void UnkUtil_DmaRun(struct UnkUtilData *);
 
+// Form changing
+void SetArceusFormPSS(struct BoxPokemon *boxMon);
+void UpdateSpeciesSpritePSS(struct BoxPokemon *boxmon);
+
 struct {
     const u8 *text;
     const u8 *desc;
@@ -6866,6 +6870,34 @@ static void ReshowDisplayMon(void)
         TryRefreshDisplayMon();
 }
 
+void SetArceusFormPSS(struct BoxPokemon *boxMon)
+{
+    u16 species = GetMonData(boxMon, MON_DATA_SPECIES);
+    u16 targetSpecies = GetFormChangeTargetSpeciesBoxMon(boxMon, FORM_ITEM_HOLD, 0);
+    if (targetSpecies != SPECIES_NONE)
+    {
+        //PlayCry2(targetSpecies, 0, 0x7D, 0xA);
+        SetBoxMonData(boxMon, MON_DATA_SPECIES, &targetSpecies);
+        UpdateSpeciesSpritePSS(boxMon);
+    }
+    /*
+#ifdef POKEMON_EXPANSION
+    u16 species = GetMonData(boxMon, MON_DATA_SPECIES);
+    u16 forme;
+    u8 abilityNum = GetMonData(boxMon, MON_DATA_ABILITY_NUM);
+    u16 ability = GetAbilityBySpecies(species, abilityNum);
+
+    if (GET_BASE_SPECIES_ID(species) == SPECIES_ARCEUS
+     && ability == ABILITY_MULTITYPE)
+    {
+        forme = GetArceusFormPSS(boxMon);
+        SetBoxMonData(boxMon, MON_DATA_SPECIES, &forme);
+        UpdateSpeciesSpritePSS(boxMon);
+    }
+#endif
+*/
+}
+
 static void SetDisplayMonData(void *pokemon, u8 mode)
 {
     u8 *txtPtr;
@@ -6952,6 +6984,8 @@ static void SetDisplayMonData(void *pokemon, u8 mode)
     {
         if (sStorage->displayMonSpecies == SPECIES_NIDORAN_F || sStorage->displayMonSpecies == SPECIES_NIDORAN_M)
             gender = MON_GENDERLESS;
+        
+        SetArceusFormPSS(pokemon);
 
         StringCopyPadded(sStorage->displayMonNameText, sStorage->displayMonName, CHAR_SPACE, 5);
 
@@ -10078,3 +10112,15 @@ static void UnkUtil_DmaRun(struct UnkUtilData *data)
         data->dest += 64;
     }
 }
+
+void UpdateSpeciesSpritePSS(struct BoxPokemon *boxMon)
+{
+    u16 species = GetBoxMonData(boxMon, MON_DATA_SPECIES);
+    u32 otId = GetBoxMonData(boxMon, MON_DATA_OT_ID);
+    u32 pid = GetBoxMonData(boxMon, MON_DATA_PERSONALITY);
+
+    // Update front sprite
+    sStorage->displayMonSpecies = species;
+    sStorage->displayMonPalette = GetMonSpritePalFromSpeciesAndPersonality(species, otId, pid);
+    LoadDisplayMonGfx(species, pid);
+}