Continuity mistake: As Jack Kelly rides the horse near the end of the "Santa Fe" sequence, his hat is waving behind him. When it cuts to a different angle the hat is on his head. Note: This was a specific detail put in by the director, symbolizing the boy's mental transition from New York to Santa Fe. However, it failed and is commonly seen as an editing mistake.
Continuity mistake: During the opening number, The kid with the brown, hard, top hat (as the boys are at the gate and when the Delancy Brothers are there) messes up the kids hair in fornt of him. When he puts his hat on correctly his hair is hanging down on the right side. Later his hat is off and when the camera switches angles a split second later, the hat returns.
Continuity mistake: During the scene in the Jacobs' house when they get out the birthday cake, Sarah takes a plate of cake and begins to hand it to Jack. After she picks up the plate, she picks up a fork, putting it in the same hand as the plate. In the next shot, she hands the same plate to Jack, but there's no fork in her hand. In fact, Jack starts to reach for the fork, only to realize that it isn't there. Sarah hands him a fork a moment later (same shot).
Revealing mistake: In the scene where Sarah (David's sister) punches one of the Delaney brothers after being harrassed in the alley, she draws back to throw a punch. She first bangs her hand on the brick wall then, after she throws the punch, she punches the other brick wall extremely hard. You can see her bend over whencing in pain and grabbing her hand right before they switch camera views. When they switch camera angles, she's no longer crouched over and she's obviously had time to recover.
Deliberate mistake: When David brings Jack home to meet the family and at the beginning of Santa Fe number.It starts raining buckets during dinner and the cake scene, but less than a minute passes and it is dry enough to sit down on the stairs at the beginning of the Santa Fe number. Then during the song "Santa Fe" and later in the dance sequence, the ground is dry as Jack is kicking up dust.
Continuity mistake: Right after Jack and David get back from Brooklyn, the newsies are standing around a statue listening to Jack tell them the results of the visit to Spot. Racetrack is smoking a cigarette. He says, "Maybe we should hold off for a while" (or something to that effect), and then puts the cigarette to his mouth. The shot changes angles and Racetrack's hand is down by his side. There's no way he could have moved that quickly.
Continuity mistake: In the opening Song "Carrying the Banner" Jack is talking to Mush and turns away from him as he is trying to button his pants, his shirt is tucked in as well. After he lathers his face and throws shaving cream at Mush he starts to sing and if you look, his pants appears buttoned and his shirt is hanging out.