Try not to feel old when we tell you this, but it's been almost 40 years since Sandy, Danny and the rest of Rydell High first appeared on the big screen.
To this day fans are still re-watching the film and arguing over which classic song is the best, but unless you're a true Grease fanatic there are some secrets about the movie you might not know.
1. Jan was really a Gray Lady
The actress who played Jan, Jamie Donnelly, started going gray in her late 20s, so she had to dye her hair during filming. But as we'll learn, she wasn't the only cast member who was a little too old to be in school....
2. The cast was almost very different
A number of actresses were in the running to play Sandy, including Marie Osmond, but princess Leia herself, Carrie Fisher, came the closest to almost getting the starring role. Henry Winkler was also almost cast as Danny. Leia and the Fonz in Grease? What a different movie that would have been!
3. These students should have graduated a LONG time ago
Most people know that Stockard Channing was really 33 years old when she played Rizzo, but the rest of the cast weren't actually kids either. Maybe they were all held back? Here's the real ages of Rydell High's students:
4. Olivia Newton-John had a wardrobe malfunction
Sandy's transformation at the end of the film surprised the audience, but the actress got a surprise of her own. The zipper on Sandy's extremely tight leather pants (which John actually owned) broke, and she had to be sewn into them before every take.