Continuity mistake: When Homer is walking to Snake Root, he has a rolling pin in his box. You can see the pin change positions in the box.
Continuity mistake: When Homer has just been given the gold medal at the National Science Fair, and he turns around to try to spot Werner Von Braun, several of the people in the crowd jump a lot closer to him when he turns back around.
Continuity mistake: When the miners decide to strike, we hear the sounds of a major storm. As they walk out the door, the rain is coming down heavily. However, in the very next shot, a long shot of the same scene, there is no rain.
Continuity mistake: When they burn down the shack where they lit off rockets, O'Dell is seen to be the last one turning around and in the next scene he turns around again.
Continuity mistake: In the first shot of the train scene there is no turn off track but in the next shot one appears outta nowhere. Hell it's even in a different spot judging by the lack of shrubbery in one of the shots.