Robin Lord Taylor, who plays The Penguin on the Fox drama, made the announcement this afternoon at New York Comic Con.
"Pee-wee Herman is playing my dad! What the hell? Oh, my God!" he exclaimed during the super-size "Warner Bros. Television Takeover" panel.
It's a return to familiar territory for Reubens, who played The Penguin's father in Tim Burton's 1992 film "Batman Returns."
"Gotham" airs Mondays at 8 p.m. ET/PT on Fox.