Revealing mistake: The opening scene shows Josh and Billy as kids walking down their street. At the end of the film, Josh is a kid again and the two are walking on the same street. The same cars are parked there, and the same woman is crossing the street at the same place. It's obvious both scenes were shot the same day. (00:03:20 - 02:06:30)
Revealing mistake: At the end of the movie when Josh and his friend are walking down the street, a lady crosses the street in front of them. Look closely to the left of the screen. The lady is obviously behind the tree waiting for her cue because she is not seen walking toward the tree before crossing the street. (02:06:40)
Revealing mistake: After young Josh is granted the Zoltar wish he drops the cable. In the following shot of him walking away not only it is not next to the machine, but it runs along the concrete, revealing it is plugged somewhere offscreen.
Answer: When Josh started at the toy company, he torpedoed Paul's skyscraper transformer by saying 'I don't get it.' Paul is returning the favor.
Brian Katcher