Continuity mistake: After the Stormtrooper tells Darth Vader the Death Star plans are not in the main computer, when Vader lifts the Rebel off his feet by his throat as the Rebel tells him they intercepted no transmissions, take note of the leg plates on the Stormtrooper to Vader's right. In the wide shot, the Stormtrooper's left leg armor does not have the knee protector plate (it looks as if it's at his right knee because the extra switched them), but in the next closeup the knee plate appears at his left knee, as it should be. The trooper also appears to go from right handed to left handed weapon carry. (00:05:40)
Continuity mistake: The headlight that is attached to the left side of the windshield frame on Medusa's motorboat, jumps to being on the right side of the frame for a shot, after the female mouse says she'd like to hit Medusa with her rolling pin. (00:37:20)
Continuity mistake: In the scene where Stromberg is thanking Dr. Bechman and Professor Marcovitz, he has a towel in his hand. When the camera changes to another angle that shows the back of his chair, his hands are totally empty and resting on an arm of the chair. Then it changes back to the original camera angle, and he now has a towel in his hands again.