The singer teamed up with more than 20 members of the Brownie guiding association in London on Friday (21Jun13) to raise money for the British branch of the United Nations Children's Fund (Unicef Uk).
She thrilled the girls, who were aged between seven and 10, by playing cards and joining in a game of Twister before leading a singalong of One Direction hits and reading a bedtime story.
Bunton says, "It was so much fun to be at the Brownies sleepover. It was absolute chaos but such a giggle. It brought back special memories of my sleepovers. My favourite part was the sing song - we all sang One Direction songs together! I don't think the girls will ever forget the excitement of tonight!"
The youngsters taking part in The Giant Sleepover with Bunton had earlier travelled to London from their homes in Fife, Scotland.