Other mistake: During "Cool," there's a shot where they're doing a sort of knee turn, and you can see Tucker Smith in the background spinning too many times (you can see him start to stick out his arms to stop himself). (01:58:20)
Maria: All of you! You all killed him! And my brother, and Riff. Not with bullets, or guns, with hate. Well now I can kill, too, because now I have hate.
Trivia: Rita Mareno was unable to hit the low notes in the song "A Boy Like That"; the entire song had to be dubbed. Natalie Wood was not told that all of her songs were going to be dubbed until after filming was completed; she went through the production thinking it would be her voice used in the songs when the film was released. Dubbing the songs after filming was completed posed an unusual problem. Normally when a song is dubbed, they play it during filming so that the actors can mouth the words so that they match the lyrics. The songs in West Side Story were dubbed after filming was completed, so it was the singers who were brought in that had to match their lyrics to the actors mouthing the words (from the documentary "West Side Memories", 2009).
Question: Why did they use actors who couldn't sing in the leading roles? Wouldn't it be easier to cast people who could sing instead of dubbing with other singing voices?