Honestly IDK for me, I mostly came from SSBB modding first before MKW, that's something I know.
Lack of new codes for the SNES Game Genie.
I printed up the Game Genie Code Creators Handbook, got a copy of the Apple IIE programmers handbook, Geiger's SNES9x debugger, and took it from there.
First game I hacked was Addams Family Values (USA) SNES.
I wanted to play custom tracks