NEW YORK -- In the Farrelly brothers' comedy Stuck on You there are actually two sets of twins. There are the conjoined brothers Bob and Walt Tenor, played by Matt Damon and Greg Kinnear, who are on all the ads and in all the film's trailers.
Then there's Cher, the evil twin of actress and singer Cher, who, as you undoubtedly guessed, is played by the entertainer known as Cher.
"When Peter and Bobby (Farrelly) sent me the script, the character was known only as The Actress. I thought it would be really cool to play this really horrible actress," recalls Cher who phoned the brothers to tell them she was definitely interested.
"Bobby was the one who set me straight when he said: 'I don't think you really understand what we want you to do. It would be so much better if you played Cher as some kind of diva monster like people did to spoof themselves on It's Garry Shandling's Show.'
"I said I would and then started waking up in the middle of the night in cold sweats, wondering what I'd got myself into. I actually tried to get out of it," admits Cher.
She couldn't break the contract, so she arrived at the Stuck on You set with great trepidation.
"Once I got over having to be horrible and mean and just be a complete bitch instead, it was kind of fun."
Among other things, the film pokes fun at Cher's penchant for dating younger men.
Her lover in Stuck on You is played by Frankie Muniz.
"I had no idea who he was except that he was famous and had this really popular TV show called Malcolm in the Middle," recalls Cher of the day she met her costar.
They were about to do a scene that finds the two of them in bed.
"This kid comes in, strips his shirt off at the same time he jumps on the bed. I thought the kid was nine years old. I turned to Peter and said: 'Can I get into trouble for this. What will his mother say?'
"Frankie told me to ask his mom who was standing just off camera."
Cher says she was relieved when Muniz proved to have a great sense of humour.
"There's this skinny kid looking at me and he says: 'I did loads of push-ups off stage so I'm really pumped. He was so funny and so adorable.
"We did a lot more than ended up in the film. I hope it all ends up in the DVD because it's racy in a really funny way."
During the filming of Stuck on You, Cher was in the middle of The Farewell Tour, so she would fly into Los Angeles on her days off.
"I was actually supposed to be finished with the tour by the time the movie started filming, but this tour has a life of its own," says Cher.
"We planned on doing 56 shows. We've already done 200 and we still have dates being added on a weekly basis."
Cher insists this really is her final tour.
"At some point, you really do have to stop touring and you'd better do it when you're still doing a good job.
"It's like Michael Jordan. If you stop and then come back and you're not as good as when you were on top, people will start comparing you to yourself. I just don't want that to happen to me."
Cher says when she has put touring behind her she will try to revive her acting career and, perhaps, her love life.
"There is no time in my life these days for romance. There hasn't been for about three years.
"I did an album and I promoted the album and then I went straight into this tour.
"In the past I've tried to have relationships while I'm touring and it just doesn't work. Guys don't like it when you go away for 14 months or when they know they are not your top priority."
It's the absence of a lover that has Cher insisting "this is a great time in my life but it is not the best. I've had more exciting times because I've had someone to share them with."
She says the '80s were the most exciting period of her life.
"I had just started in the movies and that resulted in an Oscar and I had a boyfriend who I really loved and who was really understanding of my career and was not at all frightened of being Mr. Cher."
Three years ago, director Rob Marshall was working with Cher on a TV version of the Broadway musical Mame.
"It fell through when he went off to direct Chicago. There's a chance the project will be revived with a new director. It's an intimidating role but one that definitely appeals to me."
Cher is also in talks to star in a comedy called In the Pink, about the cosmetic industry.
Simon Beaufoy, who wrote The Full Monty, has penned the latest version of this script and Tim Allen is attached as the male lead.