Ashton Kutcher, who famously is dating an older woman, now takes on interracial relationships in his new big-screen comedy, Guess Who.

This remake of the 1967 Spencer Tracy/Sidney Poitier Guess Who's Coming to Dinner casts Kutcher as a white guy who falls for Bernie Mac's black daughter. It opens March 25.

''Souls don't have a color,'' Kutcher noted at the premiere Sunday night. Upon arriving, Kutcher, 27, quickly hurried his 42-year-old lady love, Demi Moore, into Grauman's Chinese Theatre before returning to the red carpet for interviews.

Ten minutes earlier, Moore's ex-husband, Bruce Willis, had entered the theater, seemingly solo.

Kutcher wore a small, black leather pouch around his neck, which he described as ''my secret.''

''Kutch,'' who also is a producer on the film, will cross-promote Guess Who on his popular MTV prank show, Punk'd, by playing a practical joke on his Guess Who girlfriend, Zoe Saldana.

''We got Zoe good,'' he said of the episode, which is set to air Sunday night. Although he didn't want to give away the whole prank, Kutcher said it's in keeping with Guess Who's interracial dating theme. ''Zoe gets a little offended and uses a lot of swear words.''