Billy Crystal accidentally gave away his iconic 'When Harry Met Sally' sweater.

The 76-year-old star admitted he took "a lot" of his character's wardrobe from the set of the 1989 romantic comedy but he has managed to lose the white woolly knitwear as he thinks he mistakenly donated it to UCLA's drama department along with a number of other items he felt they could use for costumes.

He told People magazine: “I got a lot [of clothes from set]. I’m a little bit of a clothes horse. The one I don’t have is that sweater, and I had it for years, the one from 'Harry and Sally' — the real one."

Asked what he thinks happened to it, he added: “I made a donation. I believe it was to UCLA’s theatre department with tons of clothes for costumes. I have a feeling it’s there. I’ve racked my brain as I’ve seen other people — you’ve seen them on social media wearing a sweater, doing the pose that is from that scene. I wish I had that sweater."

The 'City Slickers' star made an appeal to the university in the hope of getting his sweater back.

He added: “UCLA, if you’re watching, maybe would you check the archives and see if it’s in the wardrobe department?”

Billy recently reflected on the enduring appeal of the movie and how so many people still view him and co-star Meg Ryan as a couple.

He said: “We were thrown together by [director Rob Reiner and screenwriter Nora Ephron], chosen to be this couple and you never know — almost 35 years later, we’re still a couple to everybody.

"As you get further along and new generations see this movie and feel it and watch it over and over again on Valentine’s Day, on New Year’s Eve, whatever it is.

"You know, people fall in love every day, and people fall out of love every day. This movie is an evergreen that way. It’s a beautiful thing."