Abbott and Costello Meet the Invisible Man (1951)

Continuity mistake: At the detective agency, while Bud and Lou are talking to the murderer, the description of the murderer comes over the police radio, and it states "5 feet 11 inches, weighs 165, blue eyes, brown hair, last seen wearing a felt hat and dark borwn overcoat". Then 15 seconds later Bud says out loud, writing on a piece of paper the description "5 feet 10 inches, weight 165, blue eyes, sandy hair".

Continuity mistake: When Bud and Lou arrive at Tommy's house for the first time, and the moth makes a spooky shadow on the flashlight, the size, shape, motion, and wing motion of the shadow on the wall are different from those of the actual moth on the flashlight.

Revealing mistake: When Lou and Tommy are in the car at the park, and Tommy is taking the disguise bandage off his head, a very faint outline of Tommy's head is visible under the incomplete special effect.

Bud Alexander: I'll have the lambchop luncheon.
Lou Francis: Um, I know what I want. Spaghetti.
Tommy Nelson: And a steak.
Waiter: [to Lou.] What do you want?
Lou Francis: Spaghetti.
Tommy Nelson: And a steak.
Waiter: [to Lou.] You said you knew what you wanted. Do you want spaghetti or steak.
Lou Francis: I'll have a spaghetti.
[Then Lou immediately raises his hand to signal Tommy not to speak.]
Lou Francis: [to the waiter.] And a steak.