Rival's effect

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Miscellaneous glitches of Pokémon Red and Blue and Pokémon Yellow

Amazing Man (Red and Blue only) | Cable Club escape glitch | Celadon looping map trick | Champion Blue music muting glitch | Coastal Flooding | Confusion and Substitute glitch | Cooltrainer move | Cycling based glitch maps | Escape sprite handling glitch | Evolve without an evolutionary stone (Red and Blue only) | Evolving Raichu (Red and Blue only) | Expanded item pack | Expanded Pokédex | Focus Energy glitch | Get stuck in a wall | Ghost Bicycle glitch | Glitch encounter system | Glitch City RAM Manipulation | Infinite Blaine Door | Introduction Nidorino glitch (Red and Blue only) | Invisible PCs (Red and Blue only) | Invisible tree glitch | Item stack duplication glitch | Mute the music in the Pokémon League | Partial trapping move link battle glitch | Pokémon Tower Pokédex glitch | PP underflow glitches | Recovery move glitch | Rival's effect | See a Ghost without a Silph Scope | Selfdestruct and Substitute glitch | Silph Co. PC Glitch | Slot machine glitch | Stand on a tree | Statue behavior glitch (Red and Blue only) | Super effective move AI flaw (Red and Blue only) | Super Glitch | Surf down glitch | Swift miss glitch | Transform assumption glitch | Transform Empty Move Glitch | Trick Zone | Vending machine purchase glitch | Walk around with only fainted Pokémon (Red and Blue only) | Walking lag glitch | Walk on water through Surf | Walking Pikachu happiness glitch (Yellow only) | Wild appeared! | ZZAZZ Glitch

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Jack redirects here. For other uses, see Jack (disambiguation).

The Rival's effect (also known as Jack) is an effect in Pokémon Red, Green, Blue, and Yellow, caused by certain glitch items that allows the player to temporarily become invisible and move through normally impassable tiles that are one or two tiles thick.

In Yellow, it is also capable of desynchronizing the walking Pikachu so that is more than one step away from the player, because Pikachu will stay when the effect is active; which is useful for the Pikawalk glitch (Pikachu off-screen glitch).

This effect is one of the first glitches discovered that allow the player to walk through walls. As such, some sources refer to items that cause this effect simply as "walk through wall items" (Japanese: 壁抜けアイテム)[1].

The glitch gets its English names because "RIVAL's" (hex:A2; Pokémon Red and Blue) and "JACK" (hex: B4; Pokémon Blue) are two of the glitch items that can activate the glitch.

Performing the glitch

The Rival's effect is activated by using a "Rival's effect item", which can be identified by adding +80 the the hexadecimal ID of an item that opens the Pokémon menu. For example, the glitch items "E tE" (hex:94) (Red/Blue) or "o" (hex:94) (Yellow) function like a Potion (hex:14) and are examples.

Any glitch item can be obtained in the English versions of Pokémon Red, Blue and Yellow using the Celadon looping map trick. In the Japanese versions, another item creation glitch must be used; due to the x-position address corresponding to a quantity and not an item.

If the item is an unterminated name glitch item, then a hex:50 tile (such as the bottom-left corner of a bush) must exist somewhere on the screen to avoid corruption after selecting it (but not using it).

List of Rival's effect glitch items

See Category:Rival's effect glitch items


  1. Face a passable tile.
  2. Use the Rival's effect item to open the Pokémon menu.
  3. Close the menus with B. The Pokémon sprites from the Pokémon menu will still show, and the player and NPCs will disappear.
  4. Try to move in the direction you want to go, until you become stuck. You may be able to pass through a tile even if it is normally impassable.
  5. Open the Pokémon menu from the start menu and close it to bring the sprites back and be able to walk again.


  • Moving in front of the locked Viridian City door while under the Rival's effect will cause Red to walk down and jump down a ledge (it may normally be impossible to make him jump by moving to another ledge). Red's shadow will show but not Red himself. If you open the menu while your shadow is showing, the shadow will be replaced with 9 and a horizontally flipped 9 in Pokémon Yellow and 9, the flipped 9 and both the 9, flipped 9 flipped vertically in Pokémon Red and Blue.
  • Using a valid item that opens the menu (such as a Rare Candy) after closing the Pokémon menu the Rival's effect glitch item brought up may make Red's sprite appear over the menu. Closing the start menus will activate the Rival's effect with Red visible on the screen (normally Red is invisible during the Rival's effect glitch). Red may be able to move facing the direction he was without turning or his sprite animating.
  • If you open the Pokédex or the Town Map immediately after using the Rival's effect item, the Pokémon menu sprites will still appear on the menu. Pressing up may make the game register it as a down press the first time. (documented by drc and Torchickens).


Certain items are part of a list of items that open the Pokémon menu[2]. Rival's effect glitch items open the Pokémon menu, but are not included on the list; meaning that when the menu is closed part of the game manages the player as if the party screen was still open[3].

These items include:

ID (Hex) ID (Dec) Item
0A 10 Moon Stone
0B 11 Antidote
0C 12 Burn Heal
0D 13 Ice Heal
0E 14 Awakening
0F 15 Parlyz Heal
10 16 Full Restore
11 17 Max Potion
12 18 Hyper Potion
13 19 Super Potion
14 20 Potion
20 32 Fire Stone
21 33 Thunder Stone
22 34 Water Stone
23 35 Hp Up
24 36 Protein
25 37 Iron
26 38 Carbos
27 39 Calcium
28 40 Rare Candy
2F 47 Leaf Stone
34 52 Full Heal
35 53 Revive
36 54 Max Revive
3C 60 Fresh Water
3D 61 Soda Pop
3E 62 Lemonade
41 65 X Attack
42 66 X Defend
43 67 X Speed
44 68 X Special
4F 79 PP Up
50 80 Ether
51 81 Max Ether
52 82 Elixer
53 83 Max Elixer

Similar walk through walls glitches

CC5C Rival's is a Pokémon Yellow exclusive glitch similar to Rival's effect. However, the glitch requires a way of locking address CC5C (wPikaPicUsedGFX) to 0x0A; hence like glitches such as Pikachu glitch emote arbitrary code execution, it currently requires arbitrary code execution to begin with.


1. Have a Pikachu with the below expression. If it does not have it, either keep making it faint (if happiness too high) or use Pikachu happiness oversight (if happiness too low) until it can have it (or manually adjust D46F to a value such as 0x4C). This also assumes that no special emotions (such as bucket Pikachu, scared Pikachu) are active.

2. Use arbitrary code execution to lock CC5C to 0x0A. OAM DMA hijacking will loop arbitrary code automatically.

3. Talk to Pikachu. A blank text box should appear.

4. Open the start menu and close it. A corrupted region should appear where the text box was, and it is now possible to walk through a limited number of walls like Rival's effect.

If the glitch is used immediately afterwards, it can cause the game to freeze with static playing. This occurs even after saving and resetting the game. To avoid this, Fly (or Teleport?) away before performing the glitch again.


  • Torchickens (documentation)