In 1977, actress Didi Conn decided to become a part of a “goofy little high school film" titled “Grease.”

The movie told the story of good girl Sandy (Olivia Newton-John) and bad boy greaser Danny (John Travolta) falling in love over the summer and how they managed to rekindle their romance while attending the same high school.

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“Grease” would premiere in theaters a year later in 1978 and become an iconic classic that’s still revered by fans today.

In honor of its 40th anniversary, Conn, who played beauty school dropout Frenchy, recently spilled some behind the scenes secrets to UK’s MailOnline.

Didi Conn as Frenchy in "Grease." (FOX)

The 66-year-old New York native claimed a then-23-year-old Travolta was instantly attracted to 29-year-old British-Australian singer John and it didn’t take much acting for the pair to showcase their electric chemistry.

“Oh yeah, [he did like her],” said Conn. “What was so much fun was that most of us were older than the characters we were playing so we just stayed in character all day long. So there was an ongoing improvisation happening so the flirting... was fine. It was the context of the characters and the storyline.

Conn also insisted that the 40th anniversary edition of the film highlights bonus features, including a different ending that was all too real.

“So the beginning of the movie Sandy and Danny are kissing and then she pulls away dramatically... [She's] sad and wondering if they’ll ever see each other again,” she explained. “Well, do they kiss in the movie again? They never.

"Grease" actress Didi Conn claimed co-star John Travolta (right) was attracted to actress Olivia Newton-John in real life. (FOX)

“Randal Kleiser, the director, thought, ‘Maybe I should make an alternative ending,” and they fly up into the sky and instead of looking back, Danny looks at Sandy and pulls her closer to him and gives her the juiciest kiss.

"You see for a moment she’s surprised and then she responds. It’s juicy and it’s great. They weren’t acting at that moment, it was like he had his chance and he was going to take it. It was real, it really was.”

And the shenanigans didn’t end among the cast when cameras stopped rolling.

“Let’s just say some of the trailers were rocking and rolling during filming,” she teased. “… I played Frenchy and Frenchy is a good friend so she wouldn’t tell.”

Conn said the cast enjoyed making “Grease” so much that they kept the celebration going even after filming was over. Conn admitted she remembered very little of the film’s wrap party after co-star Stockard Channing (Rizzo) made the cast “special brownies.”

"Grease" actress Didi Conn said co-star Stockard Channing (pictured) baked "special brownies" for the cast. (FOX)

“I don’t remember much about the wrap party because Stockard Channing gave everybody some brownies she made,” said Conn. “I really don’t remember much, just dancing and lying on the floor laughing with everybody.”

Even Travolta and Newtown were eager to suit up for their roles again in a sequel. However, Paramount ditched the idea.

“The last scene of the carnival when the boys are throwing pies at the coach, and he says, ‘I’ll see you in summer school,’ well that was to lead into a sequel called ‘Summer School,’” said Conn. “John and Olivia said, ‘Yes, we had such a good time let’s make another one right away.’ And Paramount said, ‘I don’t think this is going to go anywhere. We’re glad you all had a good time but no.’”

When “Grease” proved to be a box office success, Paramount quickly came up with the idea of “Grease 2.” However, many of the original cast, including Travolta and John, were no longer available to return.

Conn did appear in the 1982 follow-up starring Michelle Pfeiffer, Maxwell Caulfield and Lorna Luft. And despite having the double the budget of the original, “Grease 2” was a critical and box office flop.

Conn would go on to pursue a lasting acting career in both films and television. Two of her upcoming movies, “Paper Dreams” and “The Mimic” are currently in post-production.

Still, she happily remembers her time making the beloved classic.

Didi Conn today. (Splash)

“Nobody knew, but we really had a wonderful time,” said Conn. “We really did.”

When Fox News asked John in 2017 whether she ever got tired as an artist for often being recognized as good-girl-turned-bad Sandy, her answer was an instant one.

“No,” she laughed. “How many artists have the luck to be part of a movie that is still popular? I’m realistic and I’m grateful. They’ll be a point where I won’t be able to put on my heels, but right now I can still wobble around and do it!”