Eyes of the Kappa, Gate Theatre, London

As I entered the Gate Theatre, a small Japanese girl in a pink fleecy jacket was throwing herself on to a hillock covered with white fake fur, giggling, and rolling off it to rise and fall again. This winsome creature was representing a kappa, a mythical creature that is a lot less cute than she looks, as the stories in this piece, devised by the actors and director Simon Cox, reveal.

Cox says that these tales portray "a universal world of humour, wisdom and humility". I'm not so sure. None of these qualities seemed to apply to the story about a wandering samurai who approaches a house, where a man gives him a tatami mat for the night. Waking in the night, he feels that something is very wrong and stabs the mat with his sword. The house disappears, and the mat becomes a "raccoon dog'' that runs "toward the prairie, clutching his penis". Perhaps this convulses the Japanese, but I didn't even smile, and the only lesson I could derive from it was that spending the night with strange men is probably not a good idea for either sex.

Kappa seems tailored for a schools appearance under that rubric that always made my heart sink, "Folk Tales From Many Lands". Its cast certainly would please the most diversity-hungry committee: besides the girl, there is a Chinese woman, a Jewish woman, a black man, and a white-haired, white-skinned middle-aged man whose oleaginous voice and fixed smile recall those of children's TV entertainers of a generation ago.

Whether the actors can draw us into their stories hardly seems to matter, though, given the degree to which the rest of the cast pre-empts and subverts our reactions. The actors listening to the speaker laugh exaggeratedly while he talks and grins and slavers, in the manner of gloating characters in horror movies. When the story ends, they cackle and waggle their fingers; the black chap laughs hysterically at any mention of death. They also romp laboriously, waddle and crawl, each clad in a different-coloured fake-fur top and shiny trousers, like designer aliens.

Several of the stories are repetitious, involving a man whose kindness or cruelty to a bird is repaid when the bird reappears, transformed into a man or woman. After several versions of this, one can't help wondering why, for instance, a bird tormented by boys until saved by a priest cannot turn itself into a man (as it does later) and give the boys a thrashing? It's puzzling, too, that, while, in some stories, the good people prosper, in others the story is hardly a parable of western morality. One tale concerns a blind monk whose ears are torn off by the spirits. "From that day on, Hoichi No-Eyes was known as Hoichi No-Ears!'' All laugh.

As the Japanese girl and the black man scamper about at the start of the show, she comes out with a single word – "Cucumber!" – to which he responds, after some thought, "Anus!". Eyes of the Kappa doesn't include the audience in this game. A decision in which it shows wisdom indeed.

To 20 April (020-7229 0706)