Continuity mistake: During the scene where Lewis is first on the roof-top, and Mildred comes up to speak with him, the box he is sitting next to is plain wood on one side, and tallied on the other. When there is a close-up of Lewis' legs and the torn paper, when he's ripping the pages out of his book, the box has stencilled writing that is upside down. (00:06:25 - 00:18:30)
Other mistake: Right at the beginning of the movie, when Lewis's real mum picks him up from the box and hugs him, it's no more than three seconds before she hears Lewis from the future slipping on the step. She gets scared and puts baby Lewis back in the box. When Wilbur takes Lewis to meet his mum, near the end of the movie, the time his mum holds the baby is more than twenty five seconds.
Factual error: When Wilbur tosses Lewis onto the time machine, he should have broken or hit the glass covering the back half. And he is on all fours when the machine becomes visible, which shows he would have had his face hitting the driver seat, yet he scrambles back into the passenger seat without a problem, then is seen barely leaning forward to talk to Wilbur in the future.
Factual error: Goes along with the other factual error about the time machine: when Lewis falls, he falls into the bottom of the time machine, but when it becomes visible, a bit of roof is over his head. How could he go through the back half of the roof, but not all the way through the time machine? (00:20:35)
Revealing mistake: Near the end, right when "little wonders" starts, Lewis takes a moment to look at his future family, Lucille, Frannie, etc. When there's a closeup on Lewis, his memory scanner reveals a reflection of no one in the gym, except for Lewis, even though people are supposed to be standing in front of him.
Continuity mistake: In the scene after Lewis and Wilbur crash the time machine and are pushing it across a huge field, right before Lewis says "What about your parents?"the shadow of the time machine looks as if it's noon. In the next shot, when Wilbur responds "Mum never goes." the shadow is completely different.It's now to the left of the screen.
Other mistake: In the beginning, when Goob falls asleep, he misses the catch, by almost a foot or so. At the end of the movie when Lewis calls out to Goob, the ball lands on his head, and drops into his hand. Since Lewis didn't alter the timeline to where Goob is standing, (as to the part of not inventing the helping hat) Goop should have been in the same spot.Hermias Nieuwoudt