Britney Spears proved to be a saviour for her little sister Jamie Lynn - when she stepped in as a guest on her TV show after a scheduled performer dropped out.

The 11-year-old star of hit Nickelodeon comedy sketch show All That was worried about who was going to fill in - but her Crazy singer sister quickly saved the day in an episode which is set to hit screens on Saturday.

Jamie Lynn says, "We didn't plan for Britney to do it, but the musical guest dropped out and Britney said, 'I'll do it.'

"It was fun. I wasn't scared to act in front of her."