Simon Cowell, Elton, Liam Mower, Sharon Osbourne and Louis Walsh on stage; Simon, below, gets into the spirit, as he takes his curtain call.
For one night only the tables were turned on the X-Factor's judges as they risked ridicule themselves by donning tutus to join the cast of Billy Elliot at a charity gala performance on Wednesday.
Simon Cowell, Sharon Osbourne and Louis Walsh joined Sir Elton, the show's composer, and Liam Mower, one of the most popular young actors to play the title role, to mark the sale of the millionth ticket.
Simon, Sharon and Louis portrayed examiners at the Royal Ballet School during a short scene last night at Victoria Palace Theatre.
Elton called it "one of the funniest things'' he'd even seen, and said they were brilliant.
"Should they ever want to go back on stage again, they've got it made. Being in a tutu is a whole new career for Simon."
Elton himself made a brief stage appearance as a flat-capped miner from northern England.
In one early scene, Billy turned to a man behind a newspaper at the piano and asked: "So what do you reckon, Reg?"
Elton, whose real name is Reginald Kenneth Dwight, lowered the newspaper, sauntered off stage and muttered a line that was inaudible above the cheers.
In the show's production notes the 59-year-old said the film Billy Elliot, on which the musical is based, had inspired him because it reflected his own childhood.
Like Billy, who escapes the grim world of a coal mining town brought to its knees during the 1984 strikes by turning to ballet, the songster claimed music was his "passport to a better, more fulfilling life" than his working class roots may have allowed.
"Art can make you look at life in a way you never have before," he wrote.
Prior to the performance, he told the audience that being involved with the musical was one of the ''great events'' of this life, and it gave him ''much pleasure.''
The proceeds from the evening (25,000 pounds) went to children's charity The Place2Be, which works with disadvantaged children in schools across Britain.