'Dancing With the Stars': David Arquette Reveals Rob Kardashian's Secret Asset (Video)

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Newly-minted Dancing With the Stars contestant David Arquette says Ricki Lake and Rob Kardashian are his stiffest competition on the ABC show.

Lake has an advantage, according to Arquette, because she's has experience performing in musicals. He said on The Late Show With David Letterman Wednesday, "Ricki's great, she's going to be tough. She's really competitive. She was in Hairspray, she's like, 'I have no training, I have no experience.' Yeah right."

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Kardashian will be tough, says Arquette, because he's got a secret asset: his butt. "The thing about Rob is, and a lot of people don't know this -- he's got a great ass, just like his sister," said Arquette. "I'm serious, his ass is fantastic. I really think it's going to be a secret weapon."

Other topics of conversation with the giggly actor included the state of his relationship with Courteney Cox and his sobriety.

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Arquette said he and Cox are still separated but are best friends, "Courteney's great. I love her with all my heart but we have compatibility issues: I'm like wild and crazy, she's very calm and that really started becoming apparent after 11 years. She thinks I'm moody but I'm not moody!

"We grew apart and I advise everyone not to let that happen."

Arquette, who admits he's "cleaned up" after what he called a mid-life crisis, has been sober 245 days. He said he knew he had bottomed out when he broke his nose doing the kick-worm in a club, adding,  "I always look drunk, by the way."