Grease – the film responsible for catapulting the careers of Olivia Newton-John and John Travolta into superstardom – is celebrating it’s 40-year anniversary. And like all good decade-marking milestones, a cast member is now talking. In this case, Didi Conn who played beauty school dropout – and Sandy’s closest ally – Frenchy. She recently went into detail about the summer of 1977 and what really went on on the set of the iconic film – and it’s juicy.

“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,” Conn told The Sun. “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.”

It’s widely known producers sent Newton-John and Travolta on a blind date to evoke some sort of chemistry prior to filming. They needn’t as according to Conn it was definitely already present. “The chemistry between John and Olivia was real — very, very real… [But] a romance? No, no no. Just on-set.”

John Travolta and his co star Olivia Newton John in England during the week of release of the film Grease, 10th September 1978.

It was, however, the late Jeff Conaway, who played Danny Zuko’s right-hand man Kenickie, who was the biggest flirt. “He just oozed sexuality and he was an ever-ready bunny. He was just a very, very sexy guy,” said Conn. “He and [cheerleader] Patty Simcox [actress Susan Buckner] they had a lot of rehearsing, they had fun.”