Granted. Batman and the Joker end up getting zapped by a machine that switches their brains (much like Shredder and Splinter in the TMNT episode The Old Switcheroo), but it doesn't fully eliminate the evil in the Joker or the good in Batman, forcing Batman's allies and enemies to temporarily work together to get them back in their correct bodies.

I wish someone would make a mod of the 2011 version of Sonic CD to make it possible to play as Sonic with Tails following him (if Tails was unlocked already) that would be 100% compatible with the Knuckles mod that adds Knuckles as a third character (so that like in Sonic 3 & Knuckles, it would be possible to play as Sonic & Tails, Sonic, Tails, or Knuckles).