Here's a repost from 2006 as I was too lazy to come up with something new.
How do they celebrate Halloween in the DC Universe?
They put on masks and stage pranks
They put on fat suit costumes and gorilla costumes (in the DCU? Of course!)
They dress up as infants
They put on outdated clothes
They even try on fetish wear
They go to costume parties where lots of others are also dressed as heroes
They dress up as pirates, yarrrr!
They dress up as zombies. Mmmmm, brains!
They dress in drag
They dress in group costumes