One Panel #836: Introducing Tweedledum & Tweedledee

From Batman: "Tweedledum and Tweedledee" by Don C. Cameron, Bob Kane, Jerry Robinson, George Roussos and Charles Paris, Detective Comics #74 (April 1943)

This isn't really their first appearance. That would be Lewis Carroll's Through the Looking Glass. They do predate the Mad Hatter by more than a dozen years in terms of IPs stolen from Carroll, and yet, we don't see them nearly as often in modern Batman comics. In fact, the story was reprinted in World's Finest #209 under the rubric "Bureau of Missing Villains". Justice for T&T! Totally due for a comeback. Fortysome appearances for a classic Batman villain is NOTHING.*

*I am not ready to die on this hill.