Continuity mistake: When Omri receives his new skateboard as a birthday present the deck is red with two white stripes. For the rest of the film it is red with blue stripes.
Continuity mistake: When Omri opens his birthday presents, Gilly's rat in the plastic ball is on the table; two seconds later it disappears.
Continuity mistake: When Omri goes to pick up one of the figures from the cupboard, the closeup shows it on the top shelf. In the external shot he picks it up from the bottom of the cupboard.
Answer: In the books, yes. The key was a copy made for a theft, but because it was made by a psychic who practiced her craft by pouring molten lead and "reading" the shape it took upon cooling, the key was imbued with magical power. Specifically, it could be used in any "lever lock" style lock and it possessed the power to facilitate time travel derived from the psychic's ability to see the future. The cupboard itself also had the power to bring plastic things to life because the psychic's nephew, with his own latent psychic abilities, built it to contain his hatred of all things plastic (he was an out-of-business toy manufacturer who made lead soldiers around the time plastic toys became popular). He cast his hatred into the cupboard and locked it with his aunt's magic key. So now, that cupboard when used in conjunction with that key, will imbue a plastic avatar with the consciousness of a human being from some other point in time. When the key is used to lock a person inside any other sufficiently-sized container, that person's consciousness will be sent into a suitable avatar, also at another point in time.
Phixius