Flushed Away is being advertised as the new movie ”from the creators of Shrek and Madagascar,” and while that’s savvier than saying it’s ”from the bedlam-happy folks who brought you Wallace & Gromit: The Curse of the Were-Rabbit,” it isn’t honest. The latest collaboration between DreamWorks and Britain’s sublimely bent Aardman studio, Flushed Away is a true hybrid. It’s the tale of an upper-crust pet mouse named Roddy St. James (voiced by Hugh Jackman as an ingratiatingly polite nerd) who gets flushed down a toilet and into the scavenger-happy sewer world under the streets of London. The movie has the fish-out-of-water arc you’d expect in a mainstream kiddie bash, as well as a sculpty CGI sheen that engagingly mimics, without quite reproducing, the thumbprint tactility of Aardman’s clay-figure style. Yet it also has a great deal of the Aardman spirit. In the sewer, Roddy discovers a squalid, overstuffed metropolis of rodents, amphibians, and shabby discarded bric-a-brac (kitchen tools become power boats, cheap souvenirs priceless treasures), and characters who have imposing egos, whether it’s the Toad, a genocidal frog king (an operatically funny Ian McKellen), still pining for when he was Prince Charles’ pet, or a crew of maggots who burst into ”Don’t Worry, Be Happy” at just the right moment. Flushed Away lacks the action-contraption dottiness of a Wallace and Gromit adventure, but it hits its own sweet spot of demented delight.