The two guards that start to chase the stooges when they get out of their jail cell are wearing white tunics with a cross (like a Crusader's) but when they are next shown (chasing them through hallways) their tunics are dark with lions on them.
The suits of armor which Moe, Larry and Shemp begin to put on are not the same ones they are wearing when they enter the King's throne room.
Immediately after Larry's squirting glasses gag, Moe's shirt which should be soaked is perfectly dry.
The two main guards early in the film are clean-shaven, yet when they chase the Stooges inside the castle, they suddenly have mustaches and beards.
The key on a chain for the watchman's recording clock that dangles on the wall to the left of the courtyard entrance only appears when the guard is in a scene.
Moe can be seen breaking character by smiling at Shemp when he is ready to nail Moe's hat to his head.