Grease star John Travolta couldn't resist the chance to play the lead in the musical, Hairspray, even though it involved undergong a cosmetic sex change. He tells Steve Pratt how even he was fooled by the make-up and the fat suit.

Three times John Travolta was offered the role of lawyer Billy Flynn in the film version of hit stage musical, Chicago, and each time he turned it down. One reason, the star of Grease and Saturday Night Fever explained, was that he felt the best roles in the show were played by women.

So when producers Craig Zadan and Neil Meron next approached him they did a cheeky thing - they asked him to play the leading lady: fat but cheerful Edna Turnblad in the musical, Hairspray.

Not saying "yes" straight away had more to do with being nervous about following up Grease, one of the biggest musical hits of all time, than putting on a fat suit, make-up and wig to play a woman.

Travolta is following an honourable, historical tradition of men playing women. Dustin Hoffman as Tootsie and Robin Williams as Mrs Doubtfire both had big successes in gender-bending movie roles. And who can forget the classic combination of Jack Lemmon and Tony Curtis, dragged up as musicians posing as female musicians in an all-girl band to escape the clutches of gangsters?

What makes Travolta's dressing up different is that he's playing a woman, not a man dressed up as a woman as previous frock-wearers like Hoffman and Williams have been.

Hairspray's Edna has traditionally been played by a man, from the original John Waters film with professional cross-dresser Divine in the frock, to the Broadway production with Harvey Fierstein as the Baltimore mother.

Back in Shakespeare's time, men and boys played all the roles, including the female parts. These days, men mostly dress up as women for comic effect. In Hairspray, the audience are in on the joke that an actor is playing Edna but the fact that it's a man isn't alluded to at all.

Unsurprisingly, Travolta took time to accept his sex change. "It was hard for me to grasp the concept of being a leading man for 30 years, and now I'm being sought out to play a fat woman from Baltimore," he explains.

Sometimes, as the country song goes, it's hard to be a woman. Just ask Travolta, who spent four to five hours in the make-up chair at the start of his working days. He was encased from forehead-to-toe in a full 30lb body fat suit and given separate gel-filled silicone prosthetic applicances (chin and lower lip, upper lip, two cheek pieces and one wrap-around neck and cleavage piece).

People were taken in by his transformation. One audience member asked after an early screening, "who was the lovely woman who played Edna?". The producers, too, report that cinemagoers didn't know it was Travolta until they saw his name in the credits at the end.

Even the actor didn't recognise himself on viewing the screen test. "I didn't see me in it, and I tested it on other people. I said 'take a look at that. There's this broad we're looking at to see if she's going to be good for the movie'," he recalls.

"I let them watch for five minutes, and I said 'what do you think of her?'.

They said, 'she's fun, she's bubbly, she's kind of cute'. And I said, 'good, that's me'."

Harvey Fierstein, winner of a Tony Award for his performance as Edna on Broadway, was also present when Robin Williams turned into a matronly Scottish nanny called Mrs Doubtfire.

He played the make-up artist brother of the Williams character who turned him into a woman so that he/she could spend more time with his children following his split with his wife.

The film was a box-office hit, described by one critic as "a really wholesome movie about a man in a bra" and by another as the first movie to have cross-dressing as a form of marriage therapy.

Being female seems to have brought out the worst in Dustin Hoffman, when he cross-dressed in Tootsie, playing an out-of-work actor who becomes middle-aged Dorothy Michaels in order to get a part in a TV soap. The actor is known for being a perfectionist - or difficult, as some might say - on the film set. This was reflected when he appeared in drag, with the movie going through eight writers and several directors.

Hoffman wanted Dorothy to be based in reality, not a cheap drag act. The character was at least partly based on his own mother who'd nicknamed young Dustin Tootsie as a kid. Like Travolta, he tested his disguise before going before the cameras. He took his daughter, Jennifer, to school in his full Dorothy Michaels regalia and told her to introduce him as her Aunt Dorothy from Arkansas. No one guessed that the 'aunt' was an Oscar-winning actor.

Nowadays, men playing women is seen, not just as acceptable, but a way of attracting acclaim and even awards. Hard to imagine but there was some resistance to Jack Lemmon and Tony Curtis slipping into skirts as musicians fleeing the mob in Billy Wilder's comedy, Some Like It Hot. The Daily Mail thought that "no comedy dependent on men impersonating women can influence laughter for very long, certainly not for two hours". How wrong that writer was. Some Like It Hot is now considered not just a classic comedy but one of the best ever made.

Original Hairspray star Divine - Harris Glenn Milstead - made a career out of dressing as a woman, starring in a succession of John Waters-directed movies including Pink Flamingos and Female Trouble.

Actors like nothing more than dressing up and the more unlikely the cross-dresser the better the effect. British actor Terence Stamp's portrayal of a transsexual in The Adventures Of Prisciall, Queen Of The Desert was a real head-turner. He and ex-Neighbours star Guy Pearce and Hugo Weaving played drag queens on a road trip to perform at a cabaret gig in the desert. Or cocks in a frock on a rock, as he eloquently put it.

Equality demands women are allowed to dress up as men. Everyone from Barbra Streisand (in Yentl) to Mary Pickford (as Little Lord Fauntleroy) have done it. Joan Marshall played two roles - one male, one female - in 1961 thriller Homicide.

Sometimes, it can get confusing, as when Julie Andrews played a woman playing a a man pretending to be a woman in Victor/Victoria, or Gwyneth Paltrow as a girl pretending to be a boy and then playing female roles on stage for the Bard in Shakespeare In Love.

Hilary Swank won a best actress Oscar in Boys Don't Cry, the true story of Brandon Teena, a transgendered teen who preferred life in a male identity until it was discovered he was born biologically female.

But top honours go to Linda Hunt. She took home an Oscar for playing a male Eurasian cameraman in The Year Of Living Dangerously. She won the best supporting actress prize, although some thought that, more accurately, she should've won best supporting actor.

Hairspray (PG) opens in cinemas on Friday.