Didi Conn says the cast of Grease never imagined the movie would become a phenomenon that still draws families together five decades later.
The 1978 film, based on the stage musical of the same name, was nominated for an Oscar and went on to become the highest-grossing musical film at the time. It became a staple in Canadian and American households, airing on television for generations.
Conn, who played Pink Lady Frenchy, said it was the cast who "loved working together so much" that they proposed the idea of a sequel to producer Allan Carr.
Speaking to the Press Association, she said: "This all happened like the last week we were shooting, which was when we were doing the carnival scene.
"They added a scene where the boys are throwing pies at Sid Caesar, who played the coach, and they had lousy aim and he told them, 'I'll see you in summer school' to set up a sequel.
"Then Allan went to the powers that be at Paramount and said, 'hey, we did this, we set it up, let's have the money and get a sequel going', and they said, 'this is just going to be a little summer movie', and they passed."
Sequel made without the original leads
By the time the film was released, the production company attempted to bring back the lead stars John Travolta and Olivia Newton-John, but their schedules were already booked up.
"So, they did that (the 1982 sequel) without them. Paramount didn't know, and we didn't know that it was going to be such a success. We just wanted it to continue."
Conn reprised her role as Frenchy in Grease 2.
Cast stayed in character on set
During the filming of Grease, many of the cast were years older than the teenagers they were playing. Travolta was 23, Newton-John was 29 and Conn was 26.
Conn said the age differences did not faze many of the actors.
She said: "So many of the main characters had played these roles on Broadway or the national company, so they knew how to be. They knew these characters. It didn't matter how old they were. They could still rock and roll, you know.
"But what we did, which I loved doing, was that we stayed in character all the time, at lunch, in the makeup trailer or whatever. So it was a constant improvisation, and you forget your life, and you go back in time, and that's what we did, and it really helped I think."
Decades after playing Frenchy, Conn is now focused on the film's 50th anniversary in two years. She plans to mark the occasion with a cast sing-along at the Hollywood Bowl in Los Angeles, with proceeds going to charities including the Olivia Newton-John Foundation Fund and The Jett Travolta Foundation.
"My plan is to have the cast do a sing-along at the Hollywood Bowl in LA and any money we raise can go to charities including the Olivia Newton-John Foundation Fund and The Jett Travolta Foundation.
"So that's my plan, and I'm working on it, and I'm getting closer."
On the legacy of the film, Conn said she was proud to have played a part.
She added: "I just feel very, very grateful. People relate to that movie, and families watch it together and pass it down. My heart is filled with how much joy that it's brought to people, and then I get the satisfaction of seeing people happy.
"It's a movie with so much heart, and I was lucky to play a character who just wants everybody to be the best they could be."