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.
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.
Question: Not saying I'm an expert on time travel, but when Goob and 'Doris' submit the Memory Scanner as their own, shouldn't Doris immediately vaporize much like she did when Lewis said he wouldn't invent her, seeing as Lewis is still theoretically in the future and wouldn't be present in the past to invent Doris?