From the company that brought you the utopian simplicity of “It’s a Small World” comes a place where mammals of all shapes, sizes and dietary preferences not only live in harmony, but also are encouraged to be whatever they want — a revisionist animal kingdom in which lions and lambs lay down the mayoral law together, and a cuddly-wuddly bunny can grow up to become the city’s top cop. Welcome to “Zootopia,” where differences of race and species serve no obstacle to either acceptance or achievement. It is, in short, a city that only the Mouse House could imagine, and one that lends itself surprisingly well to a classic L.A.-style detective story, a la “The Big Lebowski” or “Inherent Vice,” yielding an adult-friendly whodunit with a chipper “you can do it!” message for the cubs.