Offhand you might imagine that doing an animated version of “Romeo and Juliet” with the characters played by lawn gnomes and other garden bricabrac would be a terrible idea. Now you have unassailable proof that you’d be right. “Gnomeo and Juliet” is more creepy than endearing, just another mediocre 3-D kiddie cartoon set apart from the rest only by the fact that its weirdness might actually provoke nightmares in more impressionable tykes. Certainly it won’t encourage greater appreciation for Shakespeare in anyone, young or old.

The basic premise of the screenplay (the work of a small army of writers, including director Kelly Asbury) is that the outdoor ornaments come to life only when human beings aren’t watching, a notion swiped from “Toy Story” but still durable enough to work. The further complication, however, is that two groups of such items—one decorated in blue paint and the other in red—are owned by feuding next-door neighbors, the Montagues and Capulets, on a street in Stratford-on-Avon, and they take taken up their owners’ causes by warring against one another. During one nocturnal expedition blue Gnomeo (voiced indifferently by James McAvoy, but designed to look disconcertingly like Kenneth Branagh) bumps into red Juliet (equally bland Emily Blunt, with a kewpie doll figure) and before you can blink they’ve fallen in love.

The path of their romance, of course, is not smooth. His mother Lady Bluebury (Maggie Smith) and her father Redbrick (Michael Caine) would never understand, and things aren’t helped by the interference of Gnomeo’s red nemesis Tybalt (Jason Statham) or Gnomeo’s nerdy pal Benny (Matt Lucas). Also involved are Juliet’s frog friend Nanette (Ashley Jensen), the replacement for the nurse, and a long-discarded pink lawn flamingo named Featherstone (Jim Cummings), the stand-in for the friar, as well as one monstrous lawnmower called the Terrafirminator (voiced, sort of, by Hulk Hogan).

Like so many garden settings, the movie seems to have been thrown together from leftovers from all sorts of sources. Aside from the play and “Toy Story,” the script offers lots of puerile bits of wordplay derived from famous Shakespearean quotations (including a conversation between Gnomeo and a statue of the Bard himself, voiced by Patrick Stewart) and a collection of Elton John songs redone for countless musical montages (but all managing to sound thoroughly uninspired). There are also bursts of maniacal action (races in which the gnomes use lawnmowers as their vehicles, the last-act chaos caused by the Terrafirminator) and supposedly sweet meetings between the lovegnomes. And of course there are the inevitable pop culture references and comic relief characters (Nanette and Featherstone), who frankly come across as recycled but give the piece about the only oomph it possesses.

Nor is the animation, actually the work of Canadian Starz Animation (“9”) though the movie’s being released on Disney’s Touchstone label, much to boast about. The overall design is vaguely Aardmanesque, but lead figurines are a curiously unappealing lot. True, the artists have managed to capture the rather tacky appearance of such outdoor stuff, but they haven’t been able to give much expressiveness to the various characters, except for Nanette, who’s a brassy Ethel Merman type. So it’s difficult to care whether they’re smashed into bits or live happily ever after, although you can be certain that the latter will be the case; even the stellar voice talent makes surprisingly little impression. The 3D, morever, adds little beyond a jump in the price of admission, and in fact the darkening in the images resulting from the glasses makes the movie actually look worse than it would in 2D format.

It’s hard to imagine kids being enchanted by this picture, which is derivative in so many ways it barely has an original strand of celluloid to it. Among the Shakespearean allusions strewn throughout the dialogue, one line spoken by Featherstone sticks in the mind. “A weed by any other name is still a weed,” he says. Somehow that seems a pretty appropriate epitaph for “Gnomeo and Juliet.”