"I would love a bum like yours," Carr, 35, told Kim. "If I had a bum like yours I would walk in to a room backwards: How honored are you when people say you have the best bum in the world?"
The fashionista, 31, answered, "It's weird to think of yourself like that, but I do work out all the time.
"I also think it's like an Armenian thing; it runs in the family, and we are all really curvy. So I thank my roots for giving me a big butt!"
After she bragged her derriere has "no implants," the girlfriend of rapper Kanye West challenged Carr to take the Pepsi challenge, so to say -- and he did!
The episode airs in the UK Friday.