When Eric is talking to Donna and Kitty before he leaves, the left mirror on the Vista Cruiser changes positions from down to up to down several times.
When Eric is in the Vista Cruiser talking to the video camera, you can clearly see the edges of the green screen around his face.
When coming into the Formans' living room, Donna says it is 9:15 but Kelso's watch reads 5:35.