Anachronisms: The jukebox in the diner is a 1973 Wurlizter 1050 (which copies the design of the famous 1015), yet movie is set in 1959.Continuity: In the diner, Vai turns off the lights with her elbow, despite missing the switch by six inches.
Boom mike visible: The boom mike is reflected in the jukebox when Danny tells Sandy he has an image to protect. (In the just-released Rydell High edition (10/06), the boom mike has been digitally erased).
Continuity: When Frenchie is about to pierce Sandy's ear, the bottle of wine switches between Jan and Sandy in between shots.
Continuity: Sandy's "R" streamer on her sweater at the pep rally.
Revealing mistakes: Marty's kneepad exposed when sliding at the end of the big dance.
Continuity: In the closing number, "We Go Together," Doody and Frenchy switch places between the lines, "When we go out at night/And stars are shining bright." Also, the blonde guy to the left of them goes from a sitting position to a standing position in the same error.
Audio/visual unsynchronized: In the final sequence while singing "You're the One That I Want," Danny and Sandy spin twice in the amusement park walkthrough (The Shake Shack). On the second twirl, you can tell that it is not perfectly in sync with the music.
Incorrectly regarded as goofs: The movie is set in 1959 but in some early scenes there is a fifty star flag in the principal's office. In other scenes there is a 48 star flag flying. The official flag had 49 stars for only one year, from 4 July 1959 to 4 July 1960, and this schedule was known in advance; most people probably would have just waited for the 50 star flag or bought it early if they needed to replace a flag.
Continuity: As Rizzo being escorted into the dance hall by the leader of the Scorpions, he removes his sunglasses. In the next shot, we see him remove them again.
Continuity: Sonny runs up to lift up Patty's dress at the dance, but the shot of the actual incident shows Kenickie doing the deed.
Continuity: During Summer Nights, Rizzo's shades repeatedly jump between her face and her hand between shots.
Continuity: During the last part of the racing sequence, along the river's banked edge, Leo's black convertible loses its front license plate, only to have it re-appear moments later.
Audio/visual unsynchronized: When Sandy clicks her tongue after her big change.
Audio/visual unsynchronized: At the cotton candy stand, Blanche is seen silently mouthing the question, "How many?" Moments later, from a different camera angle, the same question is asked - this time with audio intact.
Anachronisms: The TV truck (shown briefly before the scene in the gym) includes two roof-top air conditioners. These were not produced until the late 70s.
Continuity: As the Scorpions drive past the malt shop, Kenicke can be seen pointing at them and lowering his right hand twice.
Revealing mistakes: During "Greased Lightning" when the motor is dropped in the car and the fan is spinning, a string can be seen for a second making the fan spin.
Anachronisms: During Danny's attempt to play basketball you can hear a jet airplane taking off from LAX airport. Jet airplanes weren't in common use in 1959.
Continuity: During the final musical number, "We Go Together", at the carnival, the shadows on the ground change from short to long and back to short again.
Boom mike visible: When Danny is about to play basketball and the coach is talking to him you can see the boom mike's shadow behind the coach.
Continuity: During the dance scene, when the teachers are congratulating Patty and Eugene, Eugene starts waving to the students. In the next shot, when the camera is facing the stage, he and all the other students are standing still.
Continuity: When Marty and Vince are talking by a camera during "those magic changes" Marty puts her hand on the camera twice.
Revealing mistakes: When Rizzo is shuffling a pack of playing cards in homeroom, a string can be seen pulling them together.
Anachronisms: During the drag race, modern trucks and cars are seen driving on the overpass in the back ground.
Revealing mistakes: When Sonny snaps Tom's suspenders as he is walking into the gym, a very visible microphone can be seen on the top right corner, and also part of the crew can be seen in the bottom right corner.
Continuity: While in the shake shack, some of the close-ups do not match the other scenes, in the far shots there are people and trees behind the bars, in the close-ups there are neither, and also the wall colors are different between shots.
Continuity: In the dance-off, just before Cha-Cha replaces Sandy as Danny's dancing partner, there is a wide shot of Danny and Sandy dancing. In the corner you can see Cha-Cha walk out from behind some students. The camera then makes a close-up and she repeats the same movement.