David Arquette: Rob Kardashian Has a “Great Ass”

 Jason Merritt/Getty Images; Chelsea Lauren/WireImage.com

Rob Kardashian may not be happy with his juicy booty, but David Arquette thinks it's absolutely fabulous.

"The thing about Rob is, and a lot of people don't know this, but he's got a great ass just like his sister," Arquette said Wednesday on The Late Show With David Letterman.

"I'm serious! Once you see it, his ass is fantastic," the actor said of his Dancing With the Stars competitor, 24,. "And I really think it's going to be a secret weapon."

Before Arquette, 39, agreed to appear on the ABC show, he sought the advice of his 7-year-old daughter Coco (with estranged wife Courteney Cox).

"I asked her about Dancing With the Stars and she said, 'Well, initially I'm thinking no. But let me go to school and talk to Ashley about it. See what she thinks.' I was like, 'No, Coco, you can't tell anybody! I'm sworn to secrecy.' Hopefully I don't embarrass her."

Paired with pro Kym Johnson, Arquette — who celebrated 245 days of sobriety Wednesday — said he's got a lot to learn before the show premieres.

"When I dance, I look like I'm being electrocuted," he laughed. "Apparently there's no real room for that in ballroom dancing."

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