Continuity mistake: A spider web drawn by a girl near the fence disappears.
Continuity mistake: In the beginning, an overview shot of the playground and the Jets is shown, the movie then cuts to a closeup of Tony snapping his fingers. In the closeup, there is a boy riding his bike past Tony that was no where to be seen in the previous shot from above.
Continuity mistake: In the basketball field, the guy with the white t-shirt and pink vest is laying against the fence. In the next shot he is slightly turned to the right.
Continuity mistake: When the camera is zooming towards the playground, there's a guy on the right climbing the fence. He disappears from the fence half a second later.
Continuity mistake: When Glad Hand is telling them about the get-together dance at the gym, you can see A-Rab putting his arm on Action's shoulder, then in the next shot he does it again.
Continuity mistake: During the number, "Gee, Officer Krupke," Ice is standing right behind Riff, right before he sings "Dear kindly judge your honor..." then suddenly he's in the doorway of Doc's candy store.
Continuity mistake: When Maria finishes singing "I feel pretty" the purple fabric rests around her left shoulder. A frame later, from a new angle, it's resting around her arm.
Continuity mistake: At the bar, 2 of the darts are very close together in one shot, and farther apart in the next.
Continuity mistake: When the Jets are playing basketball and Bernardo catches the ball, the position of the legs of the guy in the violet shirt differ between the first and second shot.
Continuity mistake: In the bar, when the cop is asking where the fight is going to take place, he addresses a guy in the back. His position and that of his tie changes in half a second when the angle changes.
Continuity mistake: When Riff is talking with Bernardo at the bar, the first shot shows one hand bent over the table. A frame later both arms are crossed together.
Continuity mistake: In the bar, when the cop is asking where the fight is going to take place, he addresses a guy in the back. His position and that of his tie changes in half a second when the angle changes.
Continuity mistake: In the prologue, after the gangs jump over each other in the alley, Snowboy and Baby John both chase Bernardo, while A-Rab and Action go the other way to chase a different Shark. In the next shot, they are all together chasing the Shark A-Rab and Action were following.
Continuity mistake: When the camera zooms into the basketball field, the shadow of the Jets points in a 8 o'clock direction. In the close ups it's a 2 o'clock.
Continuity mistake: After the Jets and the Sharks have challenged themselves, Tony takes his right hand to his tie, but the immediate shot shows the hand by his side.
Answer: Officer Krupke and his partner pulled up in the squad car in front of Doc's earlier that night and asked the Jets why they were all there blocking the sidewalk, then mentioned that he knew they were cooking up something at the dance, and warned that he's coming back. Later, during the war council it's Lieutenant Schrank who shows up at Doc's. So how did Schrank know to show up there? Krupke could've told Schrank something may be going on at Doc's involving the two gangs.
Super Grover ★