Wallace and Gromit in A Grand Night Out Sadler's Wells at The Peacock, London
It's the oldest story in the book: boy with cheese complex meets girl who just can't stand the stuff, inadvertently foils transvestite penguin robbery plot and lives happily ever after with his wise but mute dog. For Wallace and Gromit, the world is at peace - a nice cup of tea and a slice of wensleydale (with crackers) are close at hand. But look behind you! Here comes the penguin, Feathers McGraw, bent on revenge.

A Grand Night Out finds Nick Park's Oscar-winning Plasticine creations back in their natural habitat: Forties decor meets the big-bolted consoles of Saturday matinee Flash Gordon in Wallace's latest Heath Robinsonian invention - the Pantheatricon. The contraption provides the narrative, such as it is: simply insert a novel of your choice - in this case, a melodramatic working of The Hound of the Baskervilles - set the genre display to, say, drama, and off you go.

On one level, this could be read as a knowing joke about plots within plots or a character's ontological freedom ("I can't possibly act!" "But you're the barmaid!"), but it is a metaphor for the production's weaknesses. It wants to appeal to people of all ages, drawing on the keenly observed, meticulously animated world of Park's imagination. In the end, however, it offers up not so much a greatest hits of the W&G films (as the writer Andrew Dawson intended) but a succession of sight-gags and half-jokes that rely on our knowledge of the superior celluloid version.

If the idea is to appeal to children alone, a 7.30pm performance, even one that comes in at comfortably under two hours, won't do much for receipts. Yes, under-eights will laugh at the physical buffoonery, hiss at the appearance of the dastardly penguin or sigh when our heroes fall out, but it's at the level of amateurish panto, without the verve to keep adults interested.

The performers have an uphill struggle: to breathe life into clay figures who are comfortable only in their own extraordinary, hermetic universe. Paul Filipiak plays Wallace with his trademark rambling chitchat and wide- eyed bemusement while Joyce Henderson has little opportunity to shine as Wallace's shy, monotone love interest, Wendolene. Only Russ Edwards' Gromit and Angela Clerkin as the penguin can exploit the cartoon-like potential of their silent performances. In opting for a halfway house between adhering to the Plasticine characters' mannerisms and opting for an impressionistic "essence of Park", the play again loses coherence.

The absurd but captivating world of Wallace and Gromit, its craft and its delicacy of touch are rarely sighted and, in the hands of director Martin Lloyd-Evans, the physical comedy is too often akin to the laboured pratfalls of presenters on children's TV. The Wallace and Gromit brand may be big business - "We could take the theatrical world by storm," says Wallace. "No, I don't think so," replies Wendolene.

To 10 Jan 1998. Booking: 0171-314 8800