Continuity mistake: When the young Edward Bloom is in church and is growing at a quick pace, you see his buttons fly off and hit the woman in front of him in the back of the head. She then turns around and his buttons are back.
Factual error: When Edward Bloom hits the winning shot in the basketball game, a three-point line is visible at his feet. The three-point line was not introduced until the 1970s in the newly formed ABA. It did not reach high school basketball gyms until the late 80s.
Factual error: When Ewan McGregor's young wife is hanging clothes in her backyard, a small digital satellite dish is visible on the rooftop of one of the houses in the background. This isn't something that should seem out of ordinary, except for the fact that the events in the scene were supposed to be taking place during the Korean War. These dishes weren't commonly seen on rooftops until the mid to late 90s.
Continuity mistake: When Will brings the canned drink to his father, the cushion at the foot of the bed keeps changing back and forth from smooth to wrinkled.
Continuity mistake: When Edward and Karl the giant are leaving Ed's hometown, Edward hands over his backpack to Karl as he's taking a different path. In one shot Edward is Ewan McGregor, but in the next (when he's shot from the back) he is obviously played by a child. It's probably to make Matthew McGrory look big without special effects.