Cuphead has no official online co-op (only local). However, if you use Remote Play Together or Parsec, cheat engine will desync your game from your partner’s. Expect massive lag or immediate disconnect.
Using Cheat Engine for is a common way to bypass the game's notoriously high difficulty. Since Cuphead is a single-player game, using tools like this generally doesn't lead to bans on platforms like Steam. Key Features for Cuphead 1.3.4