"By day we have flat hair, at night we stick our hair up and become superstars," shrieks the John Grimes half of Jedward, explaining the "Jedward paradox" that has seen the ridiculously quiffed twins go from X Factor flops to a bizarre phenomenon in a year. Their appalling cover versions and dodgy raps may not have set the charts on fire, but they have been touring since April, wowing pre-teen girls who wear cardboard "Jedhead" quiffs, bought for £4 in the foyer. The "singing" (a term that must be applied loosely) siblings perform in front of banks of neon lights. It's like watching a Frankenstein creation of Bros and Kraftwerk.

It is hard to decide whether Jedward are an inspired, postmodern comment on pop's intrinsic triviality, or just rubbish. However, while the pair's mutation of Queen and David Bowie's Under Pressure and Vanilla Ice's Ice Ice Baby may chill the bones of anyone over 12, the screaming never stops. Clearly, if you're nearing puberty, the sight and sound of somersaults, waggling bottoms in silver trousers and lyrics mentioning sex is very dangerous, although when the Dubliners launch into "jailbeat" anthem I Want Candy, someone should call social services.

The (gulp) two-hour marathon is exciting and appalling. The Beastie Boys' Fight for Your Right ("Mom, you're just jealous, it's the Jedward boys!") nearly causes a riot, but Matthew Wilder's Break My Stride is the musical equivalent of waterboarding. The boys grin like they're in on a huge conceptual prank, not a career. When a wig lands on the stage, one of them puts it over his dyed barnet: "In two years when my hair's fallen out, I might be needing this."

At Waterside theatre, Aylesbury (0844 871 7627), tonight. Then touring.