So this really buzzed me and I was wondering 'can we apply this to perform IDKD without ACE/Corruption?'. Originally I was about to say no because the idea is to get MORE than 6 Pokémon not just BEYOND the 6th. But then, I thought: what if we can go SO FAR BEYOND that we actually reach the Echo RAM copy of the number of Pokémon and change that value by switching the corresponding 'glitch Pokémon' with a valid Pokémon?
Some calculations later, it turns out it can be done; with this trick, the ID of a Valid Pokémon will become the number of Pokémon, and the rest is the easy part. Here's my take.
- Get 81 Hyper Potions and a Pidgey (alternatively, you can get a Magikarp and evolve it into a Gyarados).
- Trigger item underflow glitch.
- Fly to Indigo Plateau
- Don't move, open bag, switch Hyper Potion x81 with the 38th item (should be Pokédex)
- Close bag, save/reset.
- You are now in a glitch city with WTW active (map size glitch, but we don't care here). Go down to Route 23.
- Open Start Menu, press down twice, then A, to access the Pokémon Menu.
- Press up 29 times to access the proper 'glitch Pokémon' and switch it with Pidgey/Gyarados (you just have to press down once to get the cursor back to Pokémon 1).
- Switch Pokémon 1 with Pokémon 7 (yeah you can do that now)
- Close the Pokémon Menu but not the Start Menu. Save/reset (the game will most likely freeze before the reset).
- The IDKD is now active. Here's what you can do with it.
To remove IDKD, just switch back Pokémon 1 to 7 and store all extra Pokémon. With Pidgey, you have 36 Pokémon and with Gyarados, you have 22. I'm working on how to improve the setup to use a Nidoking or a Slowbro; that will give you only 7 or 8 Pokémon, but you need a $FF in some specific bytes so it's not that easy.
EDIT: A potential workaround is to use any Pokémon with ID > 6 and current HP = 255. Then, perform 2-7 switch before 1-7 switch and the rest is the same. Using Nidoking/Slowbro with this trick saves a lot of time for the price of one extra switch.