When King falls into Ann's bath water, there is splashing noise, but he gets up right away, and his coat and pants are completely dry.
At the start of the film, there's what appears to be a BEA Viscount plane in the air, giving the impression that the King is aboard, but the one that lands is a Pan American Boeing 377 Stratocruiser. He is shown getting off a third type of aircraft, a Pan Am Douglas DC-6.
When Rupert plays solitaire in Shahdov's room, the position of his hands changes between shots.
During the fire hose gag in the courtroom, the King's finger is stuck in the nozzle and in the next angle, as the water is turned on, both of his hands are grasping the nozzle. The action is presented as continuous, but there is no view of the water forcing the King's finger out of the nozzle.
The TV station repeatedly shown in the movie has the call letters "KPXA". However, being in New York, the call letters should begin with a "W" as stations east of the Mississippi River begin the letter "W" and not "K". However, there are exceptions to this "rule", such as KDKA and KQV in Pittsburgh, Pennsylvania.
When King Shahdov first meets Rupert, the boy goes into an extended diatribe. Numerous times, the boy can be observed silently saying Charles Chaplin's lines as well as his own, presumably as a way of remembering his cue.
When the king is rubbing Ann's ankle on the side of the tub, she is shown sitting at an angle where there's no way it could have been her foot. Her foot and ankle are too thick to belong to her body, and she is too far away and does not react as if he is touching her.
In the last scene with Shahdov and Jaume, the image is reversed as can be seen by the reverse writing above the emergency exit sign above them and their jacket pockets with handkerchiefs and flower lapels are on their right side.
The penultimate shot of the King and Jaume in the plane is reversed (apparently to match the closing stock footage of a plane flying over New York).
Having arrived in New York and settled into a hotel, the King is watching television, and a commercial comes on advertising the British Whitbread Beer.
Though the movie is supposed to take place in New York City, while hailing a taxi, the London car dealership of Jack Barclay is visible in the background.
During his diatribe, Rupert claims that the Roman Empire fell with the assassination of Caesar. Caesar's assassination occurred 17 years before the Roman Empire was established.