Revealing mistake: You can see the stick making the finger move when it's in the box. (00:38:20)
Revealing mistake: Upon docking the Palomino to the Cygnus, the small ship is then carried "down" to where the crew can disembark. As the Palomino is carried along, the camera follows it linearly, past the superstructure of the Cygnus. The star filled background also shifts position slightly in exact synchrony with the motion, revealing that the background is really just a short distance beyond the spaceship miniature. (00:19:30)
Revealing mistake: When the ghost (Bugs Bunny) tells Scrooge that he is going to take him to "the man in the red suit", the ghost puts his arms up but the shadow does not.