Dial M for Murder (1954)

Revealing: Just before Anthony Dawson is going to be stabbed to death by Grace Kelly with a pair of scissors, you can see for a very short moment that the scissors are already attached to his back.

Continuity: When Mark is talking to Margo early in the film in her living room, the camera shows a front view of her and she is standing in front of liquor bottles lined up on a table. Behind her, Mark is in front of the fireplace. When Tony comes home within minutes, the bar is next to the front door and the bottles are rearranged.

Continuity: When Tony talks to Lesgate about the murder plan, Tony sits on the couch with his cane resting between his legs. In the next shot, he's suddenly holding the cane in his hands under his chin.

Alfred Hitchcock's cameo in this film is one of the harder ones to spot: he appears in the photograph of Tony and Lesgate's Cambridge class reunion.

Alfred Hitchcock wanted the film to look as natural as possible, with the camera at eye level with the actors. Since movie cameras were large (especially 3D cameras), Hitch had a small trench built into the soundstage floor, so that the camera lens was, roughly, at eye level.

This was filmed in 3-D, but was not originally released in 3-D. It wasn't until after Hitchcock died that it was released in its original 3-D form.