diff --git a/include/field_effect_helpers.h b/include/field_effect_helpers.h
index 9795d96e8..528492d81 100644
--- a/include/field_effect_helpers.h
+++ b/include/field_effect_helpers.h
@@ -17,8 +17,8 @@ u8 StartUnderwaterSurfBlobBobbing(u8 oldSpriteId);
 void SetSurfBlob_BobState(u8 spriteId, u8 state);
 void SetSurfBlob_DontSyncAnim(u8 spriteId, bool8 dontSync);
 void SetSurfBlob_PlayerOffset(u8 spriteId, bool8 hasOffset, s16 offset);
-bool8 sub_8155DA0(struct ObjectEvent *);
-void sub_8155D78(struct ObjectEvent *);
+bool8 UpdateRevealDisguise(struct ObjectEvent *);
+void StartRevealDisguise(struct ObjectEvent *);
 void StartAshFieldEffect(s16, s16, u16, s16);
 void SetUpReflection(struct ObjectEvent*, struct Sprite*, u8);
 u32 StartFieldEffectForObjectEvent(u8, struct ObjectEvent*);
diff --git a/src/event_object_movement.c b/src/event_object_movement.c
index 75e4a5cd8..4f334e827 100644
--- a/src/event_object_movement.c
+++ b/src/event_object_movement.c
@@ -4396,10 +4396,9 @@ movement_type_def(MovementType_CopyPlayerInGrass, gMovementTypeFuncs_CopyPlayerI
 
 bool8 MovementType_CopyPlayerInGrass_Step1(struct ObjectEvent *objectEvent, struct Sprite *sprite)
 {
-    if (gObjectEvents[gPlayerAvatar.objectEventId].movementActionId == 0xFF || gPlayerAvatar.tileTransitionState == T_TILE_CENTER)
-    {
+    if (gObjectEvents[gPlayerAvatar.objectEventId].movementActionId == MOVEMENT_ACTION_NONE || gPlayerAvatar.tileTransitionState == T_TILE_CENTER)
         return FALSE;
-    }
+
     return gCopyPlayerMovementFuncs[PlayerGetCopyableMovement()](objectEvent, sprite, GetPlayerMovementDirection(), MetatileBehavior_IsPokeGrass);
 }
 
@@ -6577,14 +6576,14 @@ bool8 MovementAction_RevealTrainer_Step0(struct ObjectEvent *objectEvent, struct
         sprite->sActionFuncId = 2;
         return TRUE;
     }
-    sub_8155D78(objectEvent);
+    StartRevealDisguise(objectEvent);
     sprite->sActionFuncId = 1;
     return MovementAction_RevealTrainer_Step1(objectEvent, sprite);
 }
 
 bool8 MovementAction_RevealTrainer_Step1(struct ObjectEvent *objectEvent, struct Sprite *sprite)
 {
-    if (sub_8155DA0(objectEvent))
+    if (UpdateRevealDisguise(objectEvent))
     {
         sprite->sActionFuncId = 2;
         return TRUE;
diff --git a/src/field_effect_helpers.c b/src/field_effect_helpers.c
index 30eeaadfa..67a151aaa 100755
--- a/src/field_effect_helpers.c
+++ b/src/field_effect_helpers.c
@@ -32,6 +32,9 @@ static void UpdateBobbingEffect(struct ObjectEvent *, struct Sprite *, struct Sp
 static void SpriteCB_UnderwaterSurfBlob(struct Sprite *);
 static u32 ShowDisguiseFieldEffect(u8, u8, u8);
 
+// Used by several field effects to determine which of a group it is
+#define sFldEff    data[1]
+
 #define sReflectionObjEventId       data[0]
 #define sReflectionObjEventLocalId  data[1]
 #define sReflectionVerticalOffset   data[2] 
@@ -360,9 +363,6 @@ void UpdateTallGrassFieldEffect(struct Sprite *sprite)
     }
 }
 
-// Sprite data for FLDEFF_JUMP_TALL_GRASS and FLDEFF_JUMP_LONG_GRASS
-#define sFldEff    data[1]
-
 u32 FldEff_JumpTallGrass(void)
 {
     u8 spriteId;
@@ -1301,6 +1301,13 @@ u32 FldEff_BerryTreeGrowthSparkle(void)
     return 0;
 }
 
+// Sprite data for FLDEFF_TREE_DISGUISE / FLDEFF_MOUNTAIN_DISGUISE / FLDEFF_SAND_DISGUISE
+#define sState      data[0]
+#define sLocalId    data[2]
+#define sMapNum     data[3]
+#define sMapGroup   data[4]
+#define sReadyToEnd data[7]
+
 u32 ShowTreeDisguiseFieldEffect(void)
 {
     return ShowDisguiseFieldEffect(FLDEFF_TREE_DISGUISE, FLDEFFOBJ_TREE_DISGUISE, 4);
@@ -1332,10 +1339,10 @@ static u32 ShowDisguiseFieldEffect(u8 fldEff, u8 fldEffObj, u8 paletteNum)
         sprite = &gSprites[spriteId];
         sprite->coordOffsetEnabled ++;
         sprite->oam.paletteNum = paletteNum;
-        sprite->data[1] = fldEff;
-        sprite->data[2] = gFieldEffectArguments[0];
-        sprite->data[3] = gFieldEffectArguments[1];
-        sprite->data[4] = gFieldEffectArguments[2];
+        sprite->sFldEff = fldEff;
+        sprite->sLocalId = gFieldEffectArguments[0];
+        sprite->sMapNum = gFieldEffectArguments[1];
+        sprite->sMapGroup = gFieldEffectArguments[2];
     }
     return spriteId;
 }
@@ -1346,10 +1353,8 @@ void UpdateDisguiseFieldEffect(struct Sprite *sprite)
     const struct ObjectEventGraphicsInfo *graphicsInfo;
     struct Sprite *linkedSprite;
 
-    if (TryGetObjectEventIdByLocalIdAndMap(sprite->data[2], sprite->data[3], sprite->data[4], &objectEventId))
-    {
-        FieldEffectStop(sprite, sprite->data[1]);
-    }
+    if (TryGetObjectEventIdByLocalIdAndMap(sprite->sLocalId, sprite->sMapNum, sprite->sMapGroup, &objectEventId))
+        FieldEffectStop(sprite, sprite->sFldEff);
 
     graphicsInfo = GetObjectEventGraphicsInfo(gObjectEvents[objectEventId].graphicsId);
     linkedSprite = &gSprites[gObjectEvents[objectEventId].spriteId];
@@ -1357,51 +1362,56 @@ void UpdateDisguiseFieldEffect(struct Sprite *sprite)
     sprite->pos1.x = linkedSprite->pos1.x;
     sprite->pos1.y = (graphicsInfo->height >> 1) + linkedSprite->pos1.y - 16;
     sprite->subpriority = linkedSprite->subpriority - 1;
-    if (sprite->data[0] == 1)
+
+    if (sprite->sState == 1)
     {
-        sprite->data[0] ++;
+        sprite->sState++;
         StartSpriteAnim(sprite, 1);
     }
-    if (sprite->data[0] == 2 && sprite->animEnded)
-    {
-        sprite->data[7] = 1;
-    }
-    if (sprite->data[0] == 3)
-    {
-        FieldEffectStop(sprite, sprite->data[1]);
-    }
+
+    if (sprite->sState == 2 && sprite->animEnded)
+        sprite->sReadyToEnd = TRUE;
+
+    if (sprite->sState == 3)
+        FieldEffectStop(sprite, sprite->sFldEff);
 }
 
-void sub_8155D78(struct ObjectEvent *objectEvent)
+void StartRevealDisguise(struct ObjectEvent *objectEvent)
 {
     if (objectEvent->directionSequenceIndex == 1)
-    {
-        gSprites[objectEvent->fieldEffectSpriteId].data[0]++;
-    }
+        gSprites[objectEvent->fieldEffectSpriteId].sState++;
 }
 
-bool8 sub_8155DA0(struct ObjectEvent *objectEvent)
+bool8 UpdateRevealDisguise(struct ObjectEvent *objectEvent)
 {
     struct Sprite *sprite;
 
     if (objectEvent->directionSequenceIndex == 2)
-    {
         return TRUE;
-    }
+
     if (objectEvent->directionSequenceIndex == 0)
-    {
         return TRUE;
-    }
+
     sprite = &gSprites[objectEvent->fieldEffectSpriteId];
-    if (sprite->data[7])
+    if (sprite->sReadyToEnd)
     {
         objectEvent->directionSequenceIndex = 2;
-        sprite->data[0]++;
+        sprite->sState++;
         return TRUE;
     }
     return FALSE;
 }
 
+#undef sState
+#undef sLocalId
+#undef sMapNum
+#undef sMapGroup
+#undef sReadyToEnd
+
+// Sprite data for FLDEFF_SPARKLE
+#define sFinished data[0]
+#define sEndTimer data[1]
+
 u32 FldEff_Sparkle(void)
 {
     u8 spriteId;
@@ -1418,9 +1428,6 @@ u32 FldEff_Sparkle(void)
     return 0;
 }
 
-#define sFinished data[0]
-#define sEndTimer data[1]
-
 void UpdateSparkleFieldEffect(struct Sprite *sprite)
 {
     if (!sprite->sFinished)