Theme Party Idea: Batman
The theme is Batman.
As in be a version of Batman.
Not Riddler, not Joker, not Harley Quinn. But Batman.
Be regular-ass Batman, be Russian Batman, be Green Lantern Batman, be Batman ‘66, be Hipster Batman, just be Batman. I guess I leave room for Batgirl/Batwoman as well.
It would be the best party.