Catman, sometimes a joke, sometimes not. Depends on the creators' mood, I suppose.
Harley Quinn
Season Five, Episode Six.
Season Five, Episode Three.
Season Four, Episode Twenty
In a Future State, Bruce Wayne is broke and believed dead in a totalitarian...
The Joker gets what he thinks is the one way to destroy Batman entirely...
The Justice Society had a villain who was not as old as he was...
He started off as a Green Lantern foe, became a member of the Justice...
A Suicide Squad member tended to bounce around a lot.
Decades before Harley Quinn, the Joker had a decidedly different sidekick.