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The idea of DC celebrities playing themselves in movies goes back at least to broadcaster H.V. Kaltenborn's 1939 appearance in Mr. Smith Goes to Washington, but Vermont Senator Patrick Leahy has made a minor second career in film from a different angle.

He's a major Batman groupie:

The senior senator from Vermont is in a large room packed with people when an unruly citizen bursts in making loud, unreasonable demands.

Warner Brothers Pictures

The Joker (Heath Ledger) holding a knife on Senator Patrick J. Leahy, a huge fan of Batman, in the new Batman film, “The Dark Knight.”

Anyone can see that a gavel to order is not going to work with this joker. He’s harassing people, and he’s got a gun.

The senator steps forward. “We’re not intimidated by you thugs,” he says. The man, saying, “You remind me of my father — I hated my father,” grabs the senator’s head, and thrusts a knife to his face. The senator freezes, eyes wide.

Not your typical Capitol Hill brouhaha. No, this scene is pure Hollywood, straight out of the new Batman movie, “The Dark Knight.” But that really is the senior senator from Vermont: Patrick J. Leahy — Democrat, Judiciary Committee chairman and lifelong Batman fan — has a cameo in the film and gets to be held at knifepoint by Heath Ledger’s Joker.

Bam! Kapow! Biff!