The visual effects are cheesy but unrelenting in “Shorts,” which may be enough for the most undemanding tykes. But most small fry, like their elders, will probably find this newest effort from Robert Rodriguez and his own kids, who provide him with ideas, both overstuffed and, despite the profligacy, curiously tedious. As well, one might add with due respect for the fact that Rodriguez put all of it together in his Austin-based studio (just as he did the “Spy Kids” pictures and “Shark Boy and Lava Girl”), chaotic and very amateurishly played, even though there are plenty of old pros in the cast.

The title comes from the fact that the story, a modern fantasy about a “wishing rock” that falls from the sky and grants its possessor anything he wants, is told in five parts or chapters, presented not chronologically but in the order that they occur to the narrator, dorky little Toe Thompson (Jimmy Bennett). Toe lives in a Texas town dominated by the Black Box company owned by the dictatorial Mr. Black (James Spader), and his parents (Jon Cryer and Leslie Mann) are heading competing research team to improve the firm’s signature device, which can do virtually everything from communications to cheese-grating. Toe, meanwhile, is tormented not only at home by his big sister Stacey (Kat Dennings) but at school by Black’s kids Helvetica (Jolie Vanier) and Cole (Devon Gearhart).

Toe tells us of the mayhem the “wishing rock” causes when it falls into his hands; into those of his friend Loogie (Trevor Gagnon) and his two brothers; and those of Nose Noseworthy (Jake Short) and his crazily germophobic father (William H. Macy); and finally those of Helvetica and her father. These involve such CGI creations as a bunch of wall-crawling crocodiles, some little aliens in colorful spaceships, a “Transformers”-like machine made of black boxes, a giant wasp and dung beetle, and a humongous, hungry green booger. (Kids love glop, you know.) Periodically inserted into the frantic action are bits of an interlinking gag about two siblings who engage one another in a staring contest, no blinking allowed. It loses its charms, shall we say, as the movie proceeds.

The moral that Rodriguez draws from this series of episodes is clear—the old saw about being careful about what you wish for, combined with a stern warning about people being too immature to wield enormous power. And there are ancillary messages about cleanliness, the importance of the environment, and the loss of personal contact that comes with modern technology. But mostly the movie is about raucous, effects-laden slapstick, often (like kids falling from trees and windows or being hit with rocks) of unpleasantly violent sort. It might also be noted that virtually all the female characters are depicted as either airheads or harridans, while the worst of the males, apart from the Blacks, are at most lunkheads.

Still, “Shorts” might have been amusing if Rodriguez had choreographed things dexterously; as it is, perhaps because of the need to meld effects with live action, everything looks messy, and the performances are of sub-sitcom quality. That’s to be expected, one supposes, of the kids, who are largely untrained, but what explains the broad, humorless work of practiced pros like Macy, Cryer, and Spader? Their acting is the equivalent of the funny faces, goo-gooing and nutty gyrations that adults so often resort to in trying to amuse infants in their cribs.

“Shorts” is pretty impressive technically for what’s essentially a homemade movie, but honesty demands the admission that the effects are second-rate, and man-of-all-hats Rodriguez perhaps took on too much by handling the cinematography and editing as well as the script, CGI and direction. He also had a hand in the music, which gets really strange when it uses and reuses a choral mantra with the words “Helvetica Black” toward the close. By then, though, even the most tolerant viewer, toddler or otherwise, will have pretty much lost interest.

It must be admitted, though, that the “wishing rock” seems to work. I wished devoutly for “Shorts” to end, and eventually it did.