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: When Tommy is back in the city in the bar, zoning out and hearing songs in his memory, he hears Fiona sing "Waitin' for M'Dearie." Unless there were speakers in Fiona's home, turned up and pointed across the bridge, he never could have heard that song.