Pity the poor animated film that must try to avoid drowning in the tidal wave of ''Finding Nemo.'' Rugrats Go Wild is mildly amusing, but compared to Pixar's splashy fish story, the rudimentary drawings and childish gags of Nickelodeon's latest feature look, in a word, cartoonish.
The story line combines the casts of two of the cable network's tamest shows, as toddler Tommy Pickles (voiced by E.G. Daily) and the ''Rugrats'' gang are shipwrecked on an island where ''The Wild Thornberrys''' family is shooting its nature TV series. The crossover provides little more than an excuse for the Thornberrys' Dr. Dolittle-ish daughter, Eliza (former ''Party of Five'' pipsqueak Lacey Chabert), to converse with Pickles pooch Spike (Bruce Willis, sounding dog-tired).
Poop jokes abound -- ''I can't even smell my own butt,'' moans the sniffly Spike -- and parents are thrown a few bones in the form of cinematic spoofs, some less obvious (''The Poseidon Adventure'') than others (''Titanic''). The sketchy plot is also frequently interrupted by needless songs, including a painful duet by the Pretenders' Chrissie Hynde (as a leopard) and Willis, who proves he should have limited his musical career to those '80s wine-cooler commercials.
Nickelodeon might have been wiser to save its money for the fervidly awaited ''SpongeBob SquarePants'' movie rather than waste it on ''Rugrats'' (which has grown long in the tooth creatively) and ''Thornberrys'' (which was inferior in the first place). Still, if ''Nemo'' is sold out, you could do worse for a big-screen babysitter.