Continuity mistake: At the dance contest when principal McGee asks for applause for the committee who decorated the hall, someone replies "lets hear it for the toilet paper" and Eugene changes position during the following shots.
Continuity mistake: When the girls are all sitting in the outside cafeteria just before Patty Simcox comes over watch Marty. When Patty approaches she is lifting her fork to her mouth but when the shot changes she is holding out her hand to get Patty's card without having enough time to put her fork down in between.
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)
Continuity mistake: There are red and white puffy paper decorations on each side of the door entering the gym for the dance-off. However, within a few seconds, the decorations on the left side completely disappear.
Continuity mistake: When the students are dancing to "Hound Dog" at the National Dance Off, they go up to the TV camera and start waving. You can see in the crowd a girl in a blue dress jumping up and down, but when we see it on the TV from the Frosty Palace, the girl is nowhere to be seen.
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)
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: 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)
Continuity mistake: At the end of Principal McGee's final speech before the students' graduation carnival, the Principal gives Blanche a tissue and says, "Oh Blanche, stop blubbering". Blanche then puts the tissue over her nose, but in the next scene when she bursts into tears, the tissue has opened up and is covering the left side of her cheek.
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.