Like Alice down the rabbit hole, the heroes of Disney's double bill take tumbles down long, strange tunnels and emerge in fantastic worlds. "Runaway Brain," a new seven-minute Mickey Mouse cartoon, begins with the familiar, brightly colored Mickey in up-to-the-minute surroundings. As Pluto looks on, he plays a "Snow White" video game. When he needs some quick cash to take Minnie on vacation, he answers a want ad, rings a doorbell on Lobotomy Lane and falls through a trapdoor into the basement, where a mad scientist switches his brain with that of a giant monster named Julius. Mickey with a monster brain looks as if he'd stuck his tail into a light socket; his fur is ragged, his eyes are bloodshot, his teeth are sharp. He looks, oddly, like a rodent. Meanwhile, Mickey's squeaky voice comes out of the newly gentle Julius.

As it races along, "Runaway Brain" is clever and funny. It's not a brilliant Mickey, but it may seem brilliant next to the live-action feature "A Kid in King Arthur's Court," one of the weakest children's movies Disney has released in a long while.

The title explains the plot, which is loaded with possibilities. Calvin Fuller (Thomas Ian Nicholas, the star of "Rookie of the Year") is a nervous, insecure Little League player who strikes out every time. Because he's in California, an earthquake splits the ground beneath the dugout and sends Calvin hurtling down a long tunnel. He emerges in an unintentionally tacky-looking version of Camelot, and the best part of the movie is over.

"A Kid in King Arthur's Court" is sluggish and low-energy. It has some time-traveler gags that a 4-year-old will see coming, a tentative romance between Calvin and Arthur's teen-age daughter, Princess Katey (Paloma Baeza), and fake-medieval language that can annoy the whole family. Arthur (Joss Ackland) has fallen under the influence of the evil Lord Belasco (Art Malik), or as Calvin calls him in one of his liveliest lines, "the dude in the purple dress." If Calvin brings Arthur to his senses, Merlin will send the boy home.