Continuity mistake: When Freddy and Janet arrive at Lawrence's mansion as his house guests, they arrive at night. Lawrence takes them upstairs and asks Janet to waltz with him in his ballroom. The scene takes place only a few minutes after their arrival. As they begin to dance, Freddy crawls to the door and starts moaning. Lawrence then shuts the ballroom door in his face and resumes dancing with Janet. As the shot cuts back to them dancing, a large window is plainly in view and daylight is streaming in brightly through the sheer curtains.
Suggested correction: That is not sunlight. When they arrive, it is established that the house exterior is illuminated with artificial lighting. The light streaming through the window is not much brighter that the lamps in the room, which it would be if it was sunlight.
Continuity mistake: Right before Steve Martin and Michael Caine make their bet, Steve walks up to Michael sitting at a little white table. Every time the camera goes back to face Michael his handkerchief in the breast pocket of his jacket goes from sticking way out of his jacket, to barely visible.
Continuity mistake: Near the start of the movie, Marion arrives on the train to deflect Freddy away from Beaumont Sur Mer. In this scene there are four shots of her seated in the compartment. In the first three, her legs are crossed right over left, and in the fourth, left over right.
Visible crew/equipment: Upon seeing the dancers, when Freddy is rushed away in his wheelchair by Janet, the reflection of the boom operator chasing after them can be seen in the mirror on the wall that they are running along.
Continuity mistake: When Michael Caine and Steve Martin (as Ruprecht) are on the bed in Ruprecht's room, the swinging tire gains momentum and swings in a much larger arc without anyone touching it. It swings even more than when Michael Caine and his "fiancé" enter the room.
