First comic appearance: Detective Comics #74 (April 1943)
Arkham Asylum appearance: Arkham North (Entrance Gate)
The connection: Two more characters who steal their persona from nursery rhymes and Lewis Carroll books… what are the odds? Pretty high in Gotham City, we suspect. While the pair are not considered particularly insane, they do appear in the aforementioned Arkham Asylum: A Serious House on Serious Earth. In that graphic novel, they are connected by a couple of electroshock helmets, with one as the left half of the brain and the other as the right half.
So are the beanies sitting on this seesaw equally complicated? Or are they simple, silly costume hats? We may never find out.
BizarroFun Fact: In the comics, the original Tweedledum has died and been replaced by his twin brother. Both are cousins to Tweedledee.