1. An advertising copywriter and a high school art teacher created "Grease": According to Vanity Fair, "Grease" was written by Jim Jacobs, an advertising copywriter, and Warren Casey, a high school art teacher, who met through an amateur theater group in Chicago in the sixties. The two bonded over their love of doo-wop songs from the previous decade and wrote a play about high school kids from that era. "Grease" premiered in Chicago in 1971, and made its way to New York City a year later. When its film rights became available, it was purchased by Alan Carr, who produced the film.
2. The script underwent dramatic changes: Originally, John Travolta's Danny Zuko was written as a bus boy and gas-station employee who sang a song called "Gas Pump Jockey" and the Beach Boys were meant to sing "Greased Lightnin'" in a garage. Other would-be castings: Paul Lynde was almost the Rydell High principal, Detroit Tigers player Mark "The Bird" Bidrych was almost a star jock, and Donny Osmond was considered as Teen Angel.
3. Sandy and Danny were almost played by other stars: The studio originally wanted Henry Winkler to play Danny Zuko, but the "Happy Days" star passed out of fear of being typecast. Meanwhile, the actresses considered for Sandy included Carrie Fisher, Susan Dey, Deborah Raffin and Marie Osmond, who ultimately dropped out because Sandy morphed into a rebel at the end of the film. Olivia Newton-John, who ultimately played Sandy, was discovered after she sat next to Carr at a dinner party. “She had a brilliant voice, and I didn’t think there could be any more correct person for Sandy in the universe,” Travolta said. However, to accommodate the actress, the character was made Australian and the cinematographer used soft lenses to make the 29-year-old star appear younger, especially alongside Travolta, who was then 23.
4. Elvis could have been in the film: Originally, Elvis was considered a possibility to play Teen Angel, but he died in 1977, when the movie was being made. Frankie Avalon won the part instead.
5. A few of the songs were added at the last minute: The movie was almost made without its title song, which was performed by Frankie Valli, as well as "Sandy," "Hopelessly Devoted to You" and the duet "You're the One That I Want," which was written by Newton-John's songwriter John Farrar. “He played it for me and said, ‘What do you think?’ I went, ‘Oh, God, it’s amazing.’ It just had this fantastic energy," she recalled.
6. Other songs were (nearly!) cut:Stockard Channing, who played Rizzo, had to convince Carr not to cut her big solo, "There Are Worse Things I Could Do." "That’s how you know what’s inside this little person,” she said she told Carr. “Otherwise she’s just all that surface stuff.” One star who didn't get to keep his big solo? Jeff Conaway, who played Kenickie. Originally, he was meant to sing "Greased Lightning," which later went to Travolta. “I wanted the number," Travolta admitted. "And because I had clout, I could get the number."
7. A sequel other than "Grease 2" was conceptualized: Carr wanted to make a "Grease" sequel called "Summer School," which would have focused on Kenickie and Rizzo. Instead, "Grease 2" was made in 1982, though it was a commercial failure.