RANGO (PG) Animation/Western/Comedy. Featuring the voices of Johnny Depp, Isla Fisher, Abigail Breslin, Ned Beatty, Ray Winstone, Bill Nighy, Timothy Olyphant, Alfred Molina. Director: Gore Verbinski.

Computer-animated heroes come in all shapes and sizes.

A tiny clownfish called Nemo, a weedy Viking boy called Hiccup and a flatulent green ogre called Shrek overcame the odds to become unlikely masters of their destiny.

The underlying message is clear: all creatures can achieve greatness with hard work, courage and a pinch of good luck.

Director Gore Verbinski lassos this heart-warming sentiment and corrals it to the Wild West for a rootin’ tootin’ adventure in the company of a comic chameleon.

Rango is an amusing romp and John Logan’s script is peppered with earthy one-liners that should have parents and teenagers chuckling in the aisles.

However, families who are prospecting for box office gold should beware: Verbinski’s film doesn’t cater for young viewers.

There’s no slapstick, almost no cuddly critters and the tone is dark, whether it be an armadillo called Roadkill (voiced by Alfred Molina), whose middle section is squished by a tyre on the highway, or the image of several varmints with nooses around their necks, preparing to fall from the gallows.

A lonely chameleon (voiced by Johnny Depp) is stranded in the Mojave Desert, where he meets a desert iguana called Beans (Isla Fisher). She takes him to the town of Dirt, which is on the brink of collapse because the water supply is running dangerously low.

The chameleon re-christens himself Rango and pretends to be a famous gunslinger.

The townsfolk are thrilled to have found themselves a hero and Rango becomes the town sheriff.

The chameleon sets out to discover why the water supply has dried up: “I’m going to strip away this mystery and expose its private parts.”

Rango is a feast for the eyes. The animation is immaculate, right down to tiny details such as the way the characters’ fur moves in the desert wind or the glint of tears in their eyes.

Set pieces are breathlessly orchestrated including a sequence on the highway that sees the hapless hero ricochet at breakneck speed between moving vehicles.

Depp plies his usual verbal schtick as the insecure lizard with theatrical ambitions and co-stars deliver lively vocal performances including Winstone as the hard man who promises one terrified victim: “If I see you in this town again, I’m going to slice off your face and use it to wipe my unmentionables.” Yee ha ha.