WHEN a group of unknown young actors spent the summer of 1977 shooting a goofy high school movie, they had no idea it would become one of the biggest films of all time.
In fact, the "horny" cast of Grease, which made superstars of John Travolta and Australian sweetheart Olivia Newton-John, felt like they were away on a wild summer camp.
As the musical phenomenon prepares to celebrate its 40th anniversary with yet another cinema release, Didi Conn, who played beauty school dropout Frenchy, opens up for the first time about behind-the-scenes sex and just how close they got to doing a sequel with the original stars.
The New Yorker, now 66, told The Sun: "By staying in character all day that gave us the licence to be silly and goofy and horny and flirty, and just have a wonderful, spontaneous improv going all day long."
"That had really terrific results because there were some relationships that started and, let's just say, major flirting was going on. Some of the trailers were rocking. It was hot."
That flirting even extended to the two main stars, who played T-Bird leader Danny Zuko and naive Aussie Sandy Olsson.
"The chemistry between John and Olivia was real - very, very real," before hastily correcting herself and adding: "A romance? No, no no. Just onset."
The late Jeff Conaway was the most prolific shagger behind the scenes, matching his bad-boy character Kenickie.
"He just oozed sexuality and he was an ever-ready bunny," Didi said.
"He was just a very, very sexy guy.
"He and [cheerleader] Patty Simcox [actor Susan Buckner] they had a lot of rehearsing, they had fun."
Grease made its US$6 million budget back in just two days - but studio bosses had not anticipated it would become such a worldwide box office smash.
So did Didi and the other cast become rich as a result? Not a chance.
"Believe me if I'd have known this was going to be such a big hit I would have negotiated for points (a percentage of profits) but no, one flat fee and that was it."
John and Olivia, however, are thought to have become multi-millionaires thanks to a much better deal.
"They had different agents that kind of looked into the future, yeah."
Sadly for fans, the lack of early commitment from Paramount meant they ended up turning down a planned sequel called Summer School, which would have featured all the major cast members.
"Nobody knew that it was going to be the hit," Didi said.
"In the carnival scene when the boys are throwing pies at their coach, and he says, 'Oh I'll see you guys in summer school', that was supposed to be the title of a sequel that everybody had agreed that they wanted to do.
"Paramount passed on it. They said, 'Oh this movie isn't going to do anything, glad you guys are having a good time but, no.'"
In 1996, Didi came agonisingly close to getting Grease 3 made, with all the original stars, including John and Olivia, on board to return.
She remains close friends with both stars.
She published a book called Frenchy's Grease scrapbook to raise money for autism, after her son was diagnosed with the condition.
All the cast contributed and she penned a chapter, based on conversations with the fellow stars, on what the characters would all have been doing 20 years after the film ended.
Original producer Alan Carr came on board to produce it as a movie, with the cast taking only small fees and the rest of the profits going to various charities.
But Hollywood bosses refused to use the plot written by the cast, resulting in John, Olivia and Stockyard Channing, who played Rizzo, to quit.
A disappointed Didi said: "We had a great story. Frenchy was a dog groomer. Sandy and Danny were still together. It was just a lot of fun. But nobody wanted to take our ideas, they wanted to do their own."
Unfortunately as time went by John felt: 'No let's not do this, let's let everybody just savour the moment of what we created and that's that.'"