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