A few months ago I got a voicemail from my seven-year-old nephew informing me that he needed help building a satellite communication device. He had most of the necessary parts, he assured me, including aluminum foil, some wires and cables, and AA batteries. All we needed to get started was a radio or remote control.

Nothing came of our project, but the imaginative reach of his idea made me wonder: Where did this itch for invention come from? Was my sister sprinkling something in his cereal? Reading him Arthur C. Clarke at bedtime?

Jimmy Neutron: Boy Genius, in theaters December 22, begins with the question: What would happen if kids could make their parents disappear? Jimmy gets his wish but doesn't like it. But he is a boy scientist, and fashions all manner of outlandish inventions to defeat aliens, rescue his parents, and generally save the planet from evil. Reality isn't there yet, but it's close. A comparison.