Daniel Radcliffe is in the United States right now with exactly two goals.

First, to promote the soon-to-be-released "Victor Frankenstein," in which he stars with James McAvoy.

And second, to make Jimmy Fallon dance like a trained monkey and then dump pints of water over his head.

The fun started last night (Nov. 10) during Jimmy's opening monologue, when DanRad appeared in the wings to suggest, nay, command, that the "Tonight Show" host perform the "Gangnam Style" signature dance.

And after that, it was time for a few rousing rounds of Water War, which Radcliffe dominated to begin with -- but then culminated with a grand water cannon finale that left him completely soaked, and in an interesting bind when it came to his sartorial choices for the rest of the evening.

"I'm going to a premiere later," he said, "and I don't think I brought any extra underwear."