Girls Aloud needed lyric sheets for their performance at last night's Capital FM Jingle Bell Ball.
The 'Something New' group - formed of Cheryl Cole, Nicola Roberts, Sarah Harding, Nadine Coyle and Kimberley Walsh - took to the stage at the second day of the festive concert at London's The O2 but needed extra help to remember who sang what and when before they performed to a crowd of more than 16,000 fans.
Walsh said: "We needed lyric sheets for every single song - it was so funny."
Cole - who performed a solo set at the event on Saturday - added to Capital FM: "In rehearsals I was singing Kimberley's lines and she was like: 'Cheryl, you don't sing that', and I was like: 'I'm sorry'."
Nicola said: "Cheryl had like made her own part up in 'The Promise' and I was like 'I like what you've done there, freestyling."
The show marked the group's first major show since they went on hiatus in 2009, and they admit they were stricken with nerves beforehand, though they were pleased to be back.
Harding said: "It's a bit nerve-racking - but it's good to be back."
As well as Girls Aloud, stars including JLS, Miley Cyrus, The Wanted, Pink, Bruno Mars, One Direction and Rizzle Kicks took to the stage for the two-day pop event.