The Sugababes surprised audience members with a performance of an ABBA classic in London last night.
The girl group took to the stage at the Prince of Wales Theatre to join the cast of Mamma Mia! in performing a rendition of 'Dancing Queen', while wearing brightly-coloured '70s disco costumes.
Mamma Mia! was watched by stars including Dionne Bromfield and was in aid of BBC's Children In Need POP Goes The Musical.
The Sugababes' performance rounded off a musical-packed week, which has seen former Spice Girl Melanie C rock with Queen guitarist Brian May on 'We Are The Champions' during a run of hit West End musical We Will Rock You.
Stacey Solomon sang a rendition of 'For Good' during a performance of Wicked and Bromfield belted out a version of 'Why Do Fools Fall In Love' in Million Dollar Quartet.
On Wednesday, Peter Andre joined the cast of Ghost: The Musical for a performance of 'Unchained Melody'.
The musicals that have taken part in the campaign have committed to raising £100,000 for this year's BBC Children In Need fundraiser.
The Sugababes will release their new single 'Freedom' on September 25.