Trivia: John Travolta made up the "cool dude walk" that Danny uses in the first scenes, when trying to create a bad boy image.
Trivia: Olivia Newton-John had to be sewn into her trousers at the end of the film as the zipper broke. They were put on in the morning and she was not allowed to take them off or go to the restroom while they were on, as the crew would have to waste time sewing them back on.
Trivia: Jeff Conaway had to walk slightly stooped to make John Travolta appear taller.
Trivia: When a group of waitresses at the ice-cream parlour watch the National Dance Off on television, one of them says, "There's Danny and Sandy". This waitress is John Travolta's real-life sister, Ellen.
Trivia: In the stage shows before Grease was made into a film, Jeff Conaway, who plays Kenickie, played Danny and John Travolta played Doody. Richard Gere also auditioned to play Danny in the movie, but John was given the part because of his role in 'Saturday Night Fever'. Also Didi Conn, who plays Frenchy, wanted to play Rizzo.
Trivia: Jamie Donnelly (Jan) had to dye her hair black daily during the shoot as she had prematurely grey hair.
Trivia: Dinah Manoff (Marty) could not dance at all, so they left her out of all the big dance numbers.
Trivia: Stockard Channing was 33 when Grease was made, but was supposed to be playing a teenager. She was the oldest of the main cast members.
Trivia: During the song "Look at Me, I'm Sandra Dee", Rizzo (Stockard Channing) goes to a photo of Elvis Presley and sings, "Elvis, Elvis, let me be." This shot was filmed on the same day Elvis died.
Trivia: Towards the end of the film, we see a group of students rushing out of Rydell High and onto the fields for the Graduation Carnival. All of these 'students' were winners of a contest which producer Allan Carr had organised and director Randal Kleiser chose the graduation scene as the right moment.
Trivia: Singer Olivia Newton-John had hardly done any acting, and was terrified of starring in a big-budget musical. John Travolta (who was also a singer) was really supportive, and when Newton-John made a mistake during filming, he would make it look like it was his fault and take the blame for it.
Trivia: Dinah Manoff (Marty) was the only main cast member who was of high school age during filming, she was 18.
Trivia: The Saran Wrap they are wrapping the car in during "Greased Lightning" is a blatant sexual reference (check out John Travolta rubbing it on his crotch). In the 50's, Saran Wrap was often used in lieu of condoms.
Trivia: During the dance, Marty, the girl in the green strapless dress, is talking to the TV presenter next to the camera or something. Just at the end of the scene, she turns, and you can just see the top of her dress fall down quickly. It's only for half a second, so you have to look really carefully.
Trivia: The film that Danny and Sandy watch at the drive-in features Dean Martin and Jerry Lewis. Lewis was one of director Randal Kleiser's teachers at the USC in Film Directing.
Trivia: During the dance, Danny is shown dancing with Sandy and singing a portion of the song "Those Magic Changes." Sandy then says he's very good and that he should take singing up professionally. This is a reference to the fact that John Travolta played Doody on Broadway before going on to play Danny in the movie. (Doody sings "Those Magic Changes" in the stage version. The song was used as a dance number in the film).
Answer: Watched that scene again now and I just think it was poor writing (in what's still a classic film regardless). How none of the judges noticed that Cha Cha took another girl's (Sandy's) place even after she'd already been "tapped out" is another huge plot hole. Plus a lot of people in America were watching the dance on TV and it's not mentioned by anyone after this scene. 35 years later and that scene still bugs me (haha).