Continuity mistake: When Principal McGee does her announcement to all the students at the beginning of the film, you can see a flag of the United States at the far end of her desk, but when we see a close-up of the Principal, the flag is now right in front of her.
Continuity mistake: During the sleepover, Rizzo gets off of the bed with a cigarette in one hand and the wine bottle in the other. In the next shot, the cigarette and the bottle have switched places.
Continuity mistake: At the dance when they do that partner dance down the middle of the gym, as the lines form Kenickie and Cha-Cha start dancing down it, then the next shot its another couple first down it, and then a couple of shots later Kenickie and Cha-Cha start going down the lines again.
Continuity mistake: When the waitress is cleaning off the table after the kids leave, the plates on her tray all appear to be empty. But Danny's and Sandy's plates are completely full when they leave, and no one touches their food. Kenickie takes one bite of a burger on a different plate, but not nearly enough to empty it.
Continuity mistake: During the dance, there's one song where the guys stand in one line and the girls in another, and the couples take turns walking down the middle. In one shot, Danny is placing Sandy in line, and a couple (the woman has a blue dress on) is already starting down the middle. Then it cuts to another angle and no one is in the middle. Back to the first angle, and people are in the middle again.
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.
Continuity mistake: During the song Summer Lovin', Rizzo lies down on her side on a picnic bench and puts on sunglasses. In the next shot, when she kicks Sandy and another girl off the bench, the sunglasses are off. In the following shot, they are on again.
Continuity mistake: When Danny and Sandy enter the sports hall for the National Dance Off, there are four people behind them sitting on the spectator benches, but when Doody and Frenchy enter the hall in the next shot, the people have disappeared and there is now a woman in a pink dress behind the benches.
Continuity mistake: When Sandy tells Danny that he is a fake at the pep rally, we see Rizzo, Frenchie, Jan and Marty standing behind her in a line. In the next shot, Jan is standing directly behind Rizzo.
Continuity mistake: When Tom and Sandy are eating an ice-cream sundae at the ice-cream parlour, Tom gives Sandy some money for the jukebox. After Sandy gets up from her chair, Tom then sits back in his chair and he is looking forward, but in the next shot he is looking over his shoulder at Sandy.
Continuity mistake: In the scene where the whole gang meets at the diner, the waitress brings out Danny and Sandy's food, and you can see the drinks they have ordered are a dark pink colour. In the next shot that they appear, the drinks are a lot lighter shade, almost pale pink.
Continuity mistake: Rizzo is singing the Sandra-Dee song in Frenchie's bedroom. When she sits at the desk, you can just see that the chest of drawers are all closed fully behind her. However, later in the song Rizzo jumps off the bed. As she passes, then sits back at the desk, the second drawer down is now partially open. No one goes near it during this time, as all the girls in this song are on the bed.
Continuity mistake: When Jan is eating her lunch, she is joined by Marty and Rizzo. Jan then says "Did you guys get a look at Zuko this morning?" and you can see she has nothing in her right hand, but in the next shot she is holding a fork.
Continuity mistake: The TV set that is in the scene when Jan sings, "Brusha Brusha Brusha" is not the same TV that is shown when Rizzo is getting ready to go out the window during the slumber party.
Continuity mistake: At the end of the prep rally, after Sandy confronts Danny, she is leaning on a car crying. Frenchie comes up to Sandy to console her. Watch Sandy's head, in one shot her head is up then in the next it is down.
Continuity mistake: When Sonny enters the sports hall for the National Dance Off, he twangs Chisum's braces and walks towards the bandstand. Chisum is well away from the doorway at this point. However, in the next scene, Chisum is now standing near the doorway and Sonny is walking away from the bandstand.
Continuity mistake: Widescreen version: When Vince Fontaine introduces Johnny Casino & The Gamblers at the National Bandstand, Blanche is seen walking off the stage. In the next scene, she is on the stage, dancing with the band.
Continuity mistake: Once during the dancing scene you can see Vince Fontaine standing on Marty's left side, and then suddenly on her right.
Continuity mistake: In the pre-credits sequence, when Danny and Sandy on walking on the beach, Danny is on the left and Sandy is on the right. However, in the next scene, when they kiss, they have suddenly changed positions.