Continuity mistake: When Elvis is at the pool singing "you're so square baby I don't care" watch his guitar player Scotty Moore sitting behind him. They use two camera shots for the scene. In one shot he has sunglasses on, in the other shot they are gone. This happens throughout the entire song.
Continuity mistake: When Chaplin is inside the elevator, the hose changes from being tied knee level to hip level, depending on the shot.
Continuity mistake: The commandos are in the river, at night and they are setting the charges on the bridge, the variety show is going on at the same time. Between the British soldiers heads and the roof of the auditorium, the Japanese soldiers are standing in bright sunlight.
Continuity mistake: At the start of the film when Tom is doing his trial run, he is forced off the road to avoid crashing into two oncoming trucks, driven by Johnny and Red. His truck has the number thirteen number board on the front, which isn't on it during any other time during the trial run, although it's on the truck for the rest of the film.
Continuity mistake: When Allison arrives at the island in his raft, he sticks out his head to take a look. When his face is seen, his hair is completely dry, but when his back is seen as he prepares to go ashore, his hair is soaked.
Continuity mistake: In the first few scenes in the lobby of the Contention City Hotel, the clock is silent. In later scenes, it is ticking quite loudly.
Continuity mistake: According to one of the characters, the firing squad is drawn from the 3rd Battalion of the 701st Infantry Regiment, the same regiment as most of the other characters. However, all the members of the firing squad (except the officer and sergeant, who are credited characters seen elsewhere in the film) have "710" on their collar patches. This can be seen when the sergeant, who has "701" on his collar patches, is briefing them.
Continuity mistake: Early in the film, Henry Fonda and another juror are in the men's room. When the other juror exits, the door is a swinging door. From the jury room the door is a regular door with a door knob. You can hear the door close when Henry Fonda exits and closes the door.
Continuity mistake: Sgt. Killian is wearing his helmet, but when the North Korean soldier kills him from behind, his helmet is on the ground.
Continuity mistake: The Sergeant (played by Karl Malden) is on leave with his family when the car needs water. His daughter (played by Natalie Wood) gets out and refills the water. During the conversation, Malden is bare headed, then immediately after he has a hat on.
Continuity mistake: The character Sid Sorokin sings the song "Hey There" into a dictograph machine. He then plays it back and sings a "duet" with himself. However, the lyrics and melody at the end of the song are different from what he sang into the machine originally.
Continuity mistake: When Travis finds Arliss and Old Yeller in the drinking water, he throws a rock at Old Yeller. Old Yeller is wet all over. Arliss then throws a rock back at Travis, and a chase ensues. After their mother breaks up the fight, she admonishes Travis. Travis then says something to Old Yeller. Old Yeller is lying on the ground dry as he can be. He was just in the water a little over a minute ago, yet there is no sign of wetness at all in his fur. (00:15:45 - 00:17:11)