Using two tricks for Pokémon Yellow and Pokémon Red, we can enter the Cable Club without a Link Cable.
The map numbers for Cable Club Trade Center and Cable Club Colosseum are 239 ($EF) and ($F0) respectively.
Warping to the room through the manipulation of item 36's quantity; "exit destination" (D365) typically results in a Glitch City.
However, if the "event displacement" pointer responsible for map blocks on the screen is set to 0B C7 (little endian), we can access the real Cable Club map. The map block data for Cable Club Colosseum and Trade Center are sourced from the same location.
Procedure (Red)You will need a TM39 x11, TM31 x4, Great Ball x3 and X Attack x18.
These can be fished up with TheZZAZZGlitch's "obtain any glitch item easily" trick, also known as the Celadon looping map trick.
The item in x-coordinate's place has a quantity of either 0 or 1. It can be changed from 1 to 0 by walking north or south. This integer is a value known as "y-block".
The procedure in this video warps the player to a Cable Club Colosseum Glitch City. D35F, D360 ("event displacement" pointer) is then manipulated to 0B E7 (little endian).
Since D35F is represented as an item quantity, D35E (current map number) must be an item that has to get changed for logistical purposes - swapping two items of the same type results in the game trying to merge the stacks. D35E (the item before 0B) is set to the Cable Club Colosseum Trade Center map (EF).
0B E7 works like 0B C7 because EXXX marks the Echo RAM for CXXX. TM31 (E7) is used, as the quantity is set to x4 and HM04 (C7) normally cannot have its quantity set to x4 without complication.
TM31's quantity of x4 is placed into D361 (current y-position). Great Ball (03) x 0 is placed into D362 (current x-position) and D363 (current "y-block" value).
X Attack x18 (41 12) is placed as the item and quantity representing the level-script pointer. This causes the game to run existing code at 0:1241 that makes the game load the map with the changed "event displacement" data.
Steps1) Set up an expanded items pack (e.g. with dry underflow)
2) Toss 16 of item 36 (normally a Master Ball or "!j", (Red), "x" (Yellow) from Red's house 1F to warp to the Cable Club Colosseum to obtain a quantity of 240 (256-16). This quantity represents an 'indoor' map exit destination. If you are in another map, then the item 4 spaces above is usually (sound bank 'item') x 0 and can be swapped into item 36 to obtain the initial quantity of 256. The 'sound bank item' is Ultra Ball for the overworld, but at certain 'caves, dungeons' it is an Old Amber. The Old Amber cannot be used as it is a key item. The quantity x0 represents a 'screen colours' address that is usually 0 unless you are in Rock Tunnel.
3) Swap TM40 x27 (item 33) with a TM39 x11 .
4) Swap Thunderbadge (item 34) with a TM31 x4.
5) Swap Volcanobadge (item 35) with a Great Ball x3
6) Swap 'Pokédollar symbol' (item 41) with an X Attack x18
7) Close the menu to end up in the Cable Club Colosseum.