The actor and his fiancée have date night. Plus: Mariah Carey, Jessica & Ashlee Simpson and more

UNDERDRESSED TO IMPRESS

She's just following the rules! Paris Hilton makes her entrance at Hugh Hefner's 80th birthday party Saturday, where the dress code at the Playboy Mansion called for lingerie and pajamas. Other celebs in attendance at the Beverly Hills bash: Ryan Seacrest, Maroon 5's Adam Levine and Owen Wilson.