Kristen Bell wants her bottom to resemble ''two round cupcakes''.

The 31-year-old actress - who strips down to her underwear in new movie 'House of Lies' - admitted she upped her exercise regime when she found out she would be stripping off, but said those who expect to see her fully nude can ''dream on''.

She said: ''I want two round cupcakes, always. I kicked my buns and abs sets into high gear when I knew I'd have to be in my bra and underwear on 'House of Lies'.

''But I don't show my crack! All the Mr. Skins of the world are like, 'Ooh, Kristen gets naked!' I'm like, 'Dream on!'''

It would appear Kristen's fiance, Dax Shepard, is also a fan of her ''cupcake'' rear, as she joked that the couple ''nauseate'' themselves with how ''mushy'' they can be.

She added in an interview with Women's Health magazine: ''We nauseate ourselves with how mushy we are.''

Despite the 'Forgetting Sarah Marshall' star's romantic personality, she admitted she has a ''potty mouth'' when it comes to swearing.

She explained: ''I have a potty mouth. I'm not afraid to drop an F-bomb. I can love organic tomatoes and swearing - the two aren't mutually exclusive.''