Continuity mistake: Sandy walks over to meet the girls after doing a cartwheel. On Sandy's cheerleading uniform, there is a LONG red string right next to the letter on her shirt. Then, suddenly, the string disappears in the very next shot. Then in the scene after that it is back again, and then the string is back on her shirt. (00:22:20)
Continuity mistake: During the slumber party at Frenchie's, when Rizzo brings out the wine, check out the junk on the headboard. Later in the scene when Marty is putting on her robe, the headboard is clear and now has a black fan on the left. Then even later when Jan says "You ain't getting your hands on my ears" the headboard is cluttered again, with the black fan too. (00:27:35)
Continuity mistake: In the Greased Lightning dance scene, look just in front of the last white desk on the right side during the dream car segment. One of the dancers knocks a tyre off a stand and it falls in front of the desk. A shot or two later, the tyre is back up on the stand. (00:40:05)
Continuity mistake: When Kenickie says to Rizzo in the soda parlour, "How about if I finish with you, huh?" there is a tomato ketchup squeezer on his side of the table. In the next scene when Rizzo says, "Finish this!" and throws the glass of liquid at Kenickie, the ketchup squeezer has moved to her side of the table, and in the next scene, when Kenickie is covered in liquid, the ketchup squeezer is back in its normal position. (00:52:00)
Revealing mistake: In the soda shop, the waitress turns off the lights with her elbow because her hands are full, but she misses the light switch by 6 inches. (00:55:10)
Continuity mistake: At the beginning of the National Bandstand scene you see people filling the hat of the big "Rydell Ranger" figure with pieces of paper. During the next ten minutes the figure is often visible in the background and the hat is empty - nobody emptied it. After those ten minutes the hat has paper again and is then emptied. (00:59:00)
Visible crew/equipment: In the scene during the American bandstand, at the end of the song when the teacher is dancing in front of the band members, the crews can be seen. The dressing and the hair doesn't match Grease era at all, and someone is sitting on a director's chair as well. (01:06:20)
Continuity mistake: Once during the dancing scene you can see Vince Fontaine standing on Marty's left side, and then suddenly on her right. (01:10:16)
Continuity mistake: When Cha-Cha receives the award from Principal McGee at the end of "Born to Hand Jive" at the National Dance Off, Putzie is giving Jan a piggy-back next to the Principal. However, in the next scene, Putzie is giving Jan a piggy-back right next to Cha-Cha. (01:14:00)
Factual error: The movie and events take place in 1958. However, two Fender amplifiers that are used by the band, "Johnny Casino and The Gamblers" are "Silverface" models that were only manufactured between 1967 and 1981.
Audio problem: At the cotton candy stand at the graduation carnival, Blanche is seen silently mouthing the question "How many?" In the next scene, from a different camera angle, the same question is asked - this time with audio intact.