Ryan Seacrest, Paris Hilton dress up for Halloween

Ann Oldenburg, USA TODAY

Ryan Seacrest and Julianne Hough, on the right, dress as Bonnie and Clyde for Halloween. That's Warren Beatty and Faye Dunaway on the left, from the movie.

The Halloween fun has begun, with a slew of stars dressing up.

Paris Hilton is Alice in Wonderland; her boyfriend, River Viiperi, is the Mad Hatter.

Ryan Seacrest shared a photo of himself with girlfriend Julianne Hough doing their best Bonnie & Clyde impersonation.

Julianne's Dancing With the Stars pro brother, Derek Hough, also shared a photo of them, and him, wielding a light saber. Luke Skywalker?

Kim Kardashian was a mermaid for a New York party on Saturday. Fergie and Josh Duhamel also sported costumes.

Paris Hilton chose to be a sexy Alice in Wonderland to boyfriend River Viiperi's Mad Hatter on Saturday. She dressed up a second time on Sunday night for "round 2."

And Heidi Klum, who has always celebrated Halloween in a big way, plans to be Cleopatra for 2012.

UPDATE: Klum announced Tuesday that in the wake of Hurricane Sandy, which hit the East Coast Monday night, she's canceled and will postpone her Halloween bash this year. "Hope you & your loved ones are safe after the storm," she tweeted. "Canceling my Halloween party...postponing to a haunted Christmas."

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