I wanna Picture, I wanna Rose Gear, I wanna be the LoveTrap, I wanna be the Device and I wanna be the OneLife all have boss rushes featuring buffed versions of the regular bosses found in those games, but with the exception of Picture, they're optional.
I wanna be the Forehead 2 has an optional EX boss rush with harder versions of bosses from the creator's previous games.
I wanna Scribble has a classic, Megaman-style boss rush but you only have one life. I wanna Classic also has a boss rush with original bosses that you have to clear in one go.