Ant and Dec's audition fools Pop Idol's Mr Nasty

Ant and Dec got one over on Pop Idol's Mr Nasty Simon Cowell - by auditioning for the US version of the show in disguise.

The pair donned wigs and prosthetic make-up to fool Cowell into thinking they were brothers bidding for chart stardom on American Idol.

And their disguise was so convincing that the music mogul had no idea he was gazing at the Pop Idol presenters.

Before they started, the duo dedicated their song to "Randy" and Jackson thanked them for the gesture. But Dec told him: "No, Randy's our dog. He choked to death on a rabbit."

They performed a cringe making rendition of Opposites Attract, a hit for fellow judge Paula Abdul, as Cowell watched in horror.

He was all set to deliver one of his trademark putdowns when Ant and Dec launched into a dance routine so bad that he finally started to smell a rat.

The pair then revealed their true identity and a stunned Cowell could only say: "Oh my God, I don't f**king believe it."

Ant said: "Simon said afterwards he'd thought 'hey, this guy looks a bit like Ant', but never thought it would be us - until we started dancing like loons and then I think he sussed it."

Viewers will see the stunt on the primetime show Ant & Dec's Saturday Night Takeaway, which returns for a second series this weekend. It is part of a new section called Ant & Dec Undercover, in which the boys adopt various disguises to fool the public and celebrities.

The pair travelled to Texas on the last day of auditions for American Idol's second series. They claimed to be Jimmy and Scott Osterman, two brothers from Denver, and turned up in Bill and Ted-style disguises.