Revealing mistake: When all four actors are up on the rooftops, look closely at them when they all step onto the smoke platform that brings them down. All four actors are doubles. (01:46:50)
Revealing mistake: Whenever Rudolph is walking you can see the tracks he makes before he even puts his feet down.
Revealing mistake: When the genie (Burl Ives) moves the fire plug you can see a bracket holding it up and running down to a track beneath it.