So busy about being really, really busy, Chicken Little is a computer-animated equivalent of a child placated with sugar. It’s calm for a while, even doing what you want it to do. But after that immediate fix is gone, these walls were made for bouncin’.

The diminutive hero with a false-alarm flaw and an inferiority complex is, at least in some way, relatable to everyone. His friends are good comic relief, particularly dance-happy Fish Out of Water, who gets portable help from a water helmet. Decent sight gags sprout up three at a time. Hidden amid the gotta-go, gotta-go goods are chestnuts about parental love and communication.

All of this adds up to a solid-and-short good time for parents and kids, but it’s a clunking disappointment when the film trades early charming cuteness for more manic movement.

Alien invasion as the reason for falling sky merits only a passing snicker. For a movie in love with Steven Spielberg, the story never forces Chicken Little to be persuasive about the aliens in the way Spielberg was with Close Encounters of the Third Kind. That would be the ultimate triumph for the plucky chicken, everyone’s favorite scapegoat in the animal-populated town of Oakey Oaks.

Conked on the head by what he claims was a piece of sky, Chicken Little (expertly voiced by Zach Braff) rings the town-square bell and sets off downtown destruction that literally references Raiders of the Lost Ark. A year later, there’s a film based on his mistake, Crazy Little Chicken. It’s not wink-wink, it’s yank-yank, and the movie sometimes gets lost in this sort of meta-muck.

Things settle down after Chicken feels particularly pressed to impress his dad, Buck Cluck (Garry Marshall), following an incident with a pulled fire alarm in P.E. Buck’s baseball-hero past wouldn’t seem to be genetically passed-on. But in a moment where the movie’s mania feels right, Chicken Little becomes an unlikely hero for both the team and the town.

Leave it to that falling sky to crimp the clucker’s new style. Along with Fish, the nervous and rotund pig Runt of the Litter (Steve Zahn) and wannabe girlfriend Abby Mallard (Joan Cusack), Chicken discovers the “sky” is part of a spaceship flown by aliens crossing off planets as they go. When no one, even Buck, believes them, Chicken and his friends must take action themselves.

Aside from Braff and Marshall, the voice casting is relatively uninspired. Harry Shearer merely transplants his Kent Brockman tones from The Simpsons to a dog newscaster here. It helps that Fred Willard and Catherine O’Hara pop up with self-deprecating zest as late-movie characters.

Only the very trustworthy, or very insane, would hang their movie on a bit of dialogue spoken by Garry Marshall. But director Mark Dindal (The Emperor’s New Groove) and his committee of writers pull it off when a conversation between Buck and Chicken yields a memorable, honest apology. Of course, it’s just before Buck and Chicken climb atop a clock tower to fend off aliens.

The whole movie is filled with that sort of push-and-pull. Kids might see too much silence and thought as something they’d do in a timeout, so the alien frenzy is thrust too far forward. Chicken Little still is fun, even if you don’t quite believe all that it’s telling you.