The Celadon looping map trick is a method of obtaining any glitch item in English/non-English European Pokémon Red, Blue, and Yellow
(with the exception of CANCEL/TM55 (0xFF)).
It was documented by TheZZAZZGlitch, and it mainly abuses the fact that the phantom quadrant of Celadon City is particularly easy to navigate, allowing the player to walk freely on a horizontal line covering a wide range of X-coordinates. As the player's X-coordinate represents an item in the player's expanded item pack, this translated to a wide range of items.
The trick does not work as well in the Japanese versions, as the X-coordinate represents a quantity rather than an item in these versions, and the glitch city quadrant, with the Y-coordinate out of bounds, is usually hard to navigate.
To perform this trick, one needs :
- To master the expanded item pack glitch.
- Have at least (one is best) one X Special (or item with an ID greater than 31).
- Have a stack of 255 items.
- Have two other items (labelled here item #1 and #2).
See also: Dry underflow glitch
Obtain items with an ID≥33h
The spot where the Nugget x1 will appear as item 35.
The player should arrange their item pack in this way :
Item #1 x(qty #1)
Item #2 x(qty #2)
X Special x1 (or item with ID ≥33h x1)
[items the player wants to keep or swap to obtain items]
Then, the player must toss of deposit all of items #2 then #1, and continue to toss the first item until the item counter is 1 (the first item is usable, but the second item functions as a Cancel). The pack should look like this :
X Special x1 (or item with ID≥33h x1)
[items the player wants to keep or swap to obtain items] (invisible)
The player should then toss or deposit 253 of the first item stack, then swap the first item with the second(using SELECT), twice.
If done correctly, the quantity of the first item will be adjusted to x0, and the player should be able to scroll the cursor beyond the CANCEL entry.
The player should go eastmost of Celadon City and open their menu at the bottom row of tiles (at the spot pictured). The player should then open their bag, and swap the X Special x1 (or item with ID greater than or equal to hex:33) with a Nugget x1 somewhere down.
If the menu stops responding due to the name of a glitch item, tapping B multiple times should enable it again.
The player is now able to walk right and left. The Celadon City map will be able to loop multiple times until X=hex:32 or X=hex:FF. Each right step increases the item ID of the slot where the Nugget was. Each left step decreases the item ID.
When the player receives the item they wish, it should be swapped again with the Nugget x1 (or an item that the player wants to replace). If the player uses Fly or Teleport, they can safely return to a Pokémon Center without getting trapped.
To keep the item but fix the items pack, the player should deposit the obtained item in the PC, then buy / receive three items to fix the item pack.
Obtain items with an ID≥00h
The player can stand at spots in Celadon City further to the left than the picture above to manipulate item 34 (normally the Nugget x1) to values hex:00 and hex:30, swap it to the regular item pack space and then Fly or Teleport away.
The player does not have to use Celadon City for this glitch, and it is possible to use this method to obtain any item with an ID<(map's X boundary-1).
When the menu doesn't respond due to a glitch item name, it is highly recommended that the player presses B (and not A) at a slow pace, because an accidental B press may close the menu, and a single accidental A press if a unterminated name glitch item is selected may cause the game to freeze with a chance of corrupting the save file.