Revealing mistake: In the final scene, if you look in the background that is completely opposite of the gate where the characters exit, there are two cars obviously made of cardboard. Many times they can be seen by looking over Maria's shoulder. (02:22:05 - 02:25:35)
Audio problem: During the "Officer Krupke" song, when Riff is sent to the analyst, just before the start of the verse, someone says "whoops" and it isn't part of the song.
Continuity mistake: In the "Dance at the Gym" scene, while everyone is doing a pelvic swivel with their partners, Riff's arm is around Graziella's waist. In the next shot, his arm is down. (00:32:30)
Continuity mistake: At the bar, Riff's tie when challenging Bernardo swaps from tight to loose between shots.
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: Maria prays that her brother's death is untrue, she says "Le suplico no puede ser." Her fingers are woven between each other. When they show the back shot of her, her hands are cupped and then she goes back to the previously mentioned position. (01:48:05)
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.
Audio problem: After Anita discovers Tony and Maria's tryst, Maria says "Now you know." She completely botches her Puerto Rican accent. She practically sounds British.
Other mistake: During "Cool," Baby John spins around and when he stops with his arms spread out, his right foot stumbles a little. (01:58:15)
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.
Audio problem: When the sharks are singing "We're going to hand them a surprise tonight" in the quintet version of Tonight, someone sings the wrong note on the word "Tonight". (01:33:20)
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.
Revealing mistake: When Maria is cradling the dead Tony you can see Tony's chest heave as the actor takes a breath.
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.
Answer: People would not come to the theater to see Marnie Nixon despite the fact that she has sung the lead roles in West Side Story, The King and I, and My Fair Lady. They'd rather see that darling girl from "Miracle on 34th Street" again (or Deborah Kerr or Audrey Hepburn) than an unknown with actual talent.
Myridon