When asked by a fan if he’d do his cartoon Joker voice in a mock scene from The Empire Strikes Back, actor Mark Hamill was happy to oblige. Star Wars Episode VII: The Clown Prince of Crime. That’s a movie we’d pay to see.
Here’s Emperor Palpatine in the finale of Return of the Jedi using lines spoken by Mark Hamill as the Joker. Listen closely for the other guest voice. How freaky would it be if Palpatine was actually Luke from another time?