Continuity mistake: Before Tony leaves he closes the drapes. He then says he won't go out and will stay home. She says to go out, and he agrees, so he goes to the drapes and closes them again.
Continuity mistake: There's an oscillating fan near the ceiling that alternates between running and not running from one cut to another in one scene.
Factual error: After Gene Kelly sings "The Heather on the Hill", he sees more heather on the other side of the bridge. He starts across but Cyd Charisse freezes in horror, since to cross the bridge would break the spell over the village of Brigadoon. She then drops some of her heather in the middle of the path and runs back to the village. The camera cuts to Gene Kelly chasing after her, but the heather dropped on the path has disappeared.
Continuity mistake: At one point bus driver Frankie Howard shins up a signpost to read road directions in the fog. The sign says WET PAINT and he slides down with his uniform jacket streaked and ruined. However, several minutes earlier, as he leans forward to peer into the night, Howard is already wearing the paint-stained jacket.