The first 20 minutes of this are among the funniest and most brilliant of any animated movie I've seen. Johnny Depp voices, superbly, a hapless bulging-eyed chameleon named Rango who stumbles upon authority after lying – with his forked tongue – about an heroic past as a gunslinger. The drought-afflicted desert town of Dirt makes him their sheriff, though it's a poisoned chalice given that the place is actually run by a wily old tortoise who sounds (and looks) like John Huston. The script, by John Logan, unfolds a classic Western tale that leans heavily on the plot of Chinatown. Gore Verbinski and his visual consultant Roger Deakins work marvels, both in the animal characterisation and the parched desert scrubland where most of it takes place. What children will make of in-jokes about Hunter S Thompson and Clint Eastwood is anyone's guess, but they should enjoy the magnificent setpieces – one chase involving a giant metal-beaked hawk is priceless – while Johnny Depp's puckish, free-associating spiel has an eccentric charm all of its own. It's one of his greatest roles.