Just wait until Luke Joker and Leia Quinn learn that they're brother and sister.
On second thought, I don't think that the Joker will mind.
Jen of Epbot attended the most recent Star Wars Celebration convention. She compiled the best mashup costumes there, including Captain America the Ewok, Boba Lantern and Ackbar the Ghostbuster. You can view them at the link.
Link