Actress Rebel Wilson has a fetish for smelling other stars' hair, and she has declared Brad Pitt's tresses remind her of "unicorns" after she sniffed his head at a showbiz bash.

The Pitch Perfect star was attending a Screen Actors Guild awards ceremony in Los Angeles when she was so starstruck she decided to get up close and personal with the Hollywood superstar.

Rebel admits she has a peculiar habit of smelling other famous guests' hair at awards shows, and she couldn't resist the chance to check out Brad's locks.

She tells U.K. talk show host Graham Norton, "I was at the SAG Awards and got to meet Brad Pitt but I was too nervous to say anything so I just smelt his hair. It was so embarrassing. You're really packed in like sardines and everywhere you turn there is someone mega famous and you don't know what to do so you smell their hair."

Asked by the host what aroma Brad's tresses conjured up, she replies, "Like unicorns."

The encounter is not the only time Rebel has risked embarrassing herself in front of Brad - she went in for an over-long hug after he praised her 2012 movie Pitch Perfect during a table-read for another film.

She has previously revealed, "I was sitting next to Brad Pitt and he's like, 'Uh, I've seen your movie like 20 times. My kids love it.' And he said, 'Angelina (Jolie, his wife) watches it as well.'

"I couldn't even believe he was talking to me, let alone seen me do comedy... I just kind of hugged him and for a really long extended time, to the point where he's kind of moving back. When do you get that opportunity?"

The Graham Norton interview is due to air on Friday (12Feb16).