Differences from the stage production
The order of songs was shuffled to heighten the tension of the story (e.g., the humorous "Gee, Officer Krupke", which is sung after the fatal knife fight in the play, was moved to long before the fight, and the more tense "Cool" was given the spot formerly occupied by "Gee, Officer Krupke". Due to this change, "Gee, Officer Krupke", led by Action onstage, is led by Riff in the film, and "Cool" is sung not by Riff (who is by this point dead) but by Ice (who is called "Diesel" in the stage version); Similarly, the lighthearted "I Feel Pretty" which originally was sung immediately after the fight, was moved to an earlier moment in the story, just before "One Hand, One Heart" with a few lyric changes.
Many of the lyrics were changed due to the fact they were considered unacceptable for film at the time.
Onstage, "America" is sung by Anita and Rosalia, with help from the other Shark girls. Anita sings in favor of American life while Rosalia sings positively of Puerto Rico. In the movie Bernardo replaces Rosalia in speaking negatively of America, and the Shark boys join in the song. Also, the lyrics of "America" were changed because the original lines were considered too derogatory to Puerto Rico and Latin American people in general.
Onstage, the balcony scene appears just before the song "America." In the film, it appears just afterward, giving the impression that more time has elapsed between Tony and Maria's first meeting and their duet on the fire escape.
The Song "Somewhere" was shortened and retooled for the film, in which it is sung by Tony and Maria. Onstage, "Somewhere" features a fantasy ballet sequence, in which the lights of New York fade away and the Jets and the Sharks dance together in harmony until violence breaks out, shattering the dream. The song itself is performed by the offstage voice of a young girl (in the original production, future opera star Reri Grist, who played Consuelo). Tony and Maria also have a brief introductory section of the song that was cut from the film.
Onstage, Tony is painting a new sign for Doc's store as he and Riff are talking. In the film, he is stacking crates of soft drinks.
There are 11 Jets (including Tony) and 10 Sharks in the stage version. The movie adds a 12th Jet (Joyboy) and an 11th Shark (Chile).
The Jet "Diesel" is named "Ice" in the movie. (The novel includes both names.) The Sharks named Anxious, Nibbles, and Moose are called Loco, Rocco, and Del Campo on film.
There are six Jet girls in the stage version. There are at least five in the movie, but only three are credited. (Two uncredited girls can be seen in the "Cool" sequence.) There are six Shark girls in the stage version and at least five in the movie, per the "America" number. However, the movie credits list only three girls.
In the movie Ice (Diesel) is second in command of the Jets and takes over after Riff's death. In the play, Action takes over leadership when Riff passes.
In the movie Riff says "Womb to tomb," which Tony responds "Birth to earth." In the stage production Tony responds with "Sperm to worm." This was changed due to the fact that it went far beyond censorship standards for the time.
The characters Madame Lucia and "Loud-Mouthed Crud Head" were created for the movie.
In the film, the Sharks jump Baby John and pierce his ear in the "Prologue". On stage, A-Rab is the one who gets jumped.
Tiger, Mouthpiece, Gee Tar and Big Deal are given more lines in the film.