Continuity mistake: In the prologue of the movie, two guys on the Sharks throw yellow paint on Baby John, Arab, Action, and Snowboy. When they are talking to Lt. Shrank and Officer Krupke, they are all clean, but wearing the same clothes as earlier. (00:13:05)
Continuity mistake: When the gangs are fighting in the playground, in the aerial shot you see that two of the seesaws are pointing up away from the gangs. When the Jets leave a few minutes later, all of the seesaws are pointing up away from where they were originally. (00:14:16 - 00:17:39)
Continuity mistake: In the "Dance at the Gym" scene, while everyone is doing a pelvic swivel with their partners, Riffs arm is around Graziella's waist. In the next shot, his arm is down. (00:32:30)
Continuity mistake: At the dance, when everyone is swaying with their partner, you can see both of Ice's hands on Velma's back, then in the next shot when it's following baby John, you can see Ice put his hands on her back again. (00:32:30)
Continuity mistake: In the scene right before "cool" when the two girls are crying, when they enter the garage their clothes are different.