Julia Roberts: 'I wish I'd had more notice about Taylor Swift gig'

Julia Roberts regrets dressing down for her recent night out at Taylor Swift's concert in Santa Clara, California - because the pop star pulled her up onstage.

The Pretty Woman star was backstage with her kids Phinnaeus, Hazel and Henry when Swift asked her if she'd be willing to join her and folk icon Joan Baez, and Roberts admits she didn't really have a choice.

The actress threw on a Swift tour shirt and hit the makeshift runway the singer has set up for all her 1989 tour dates.

She tells news show Extra, "I would have washed my hair. I was, like, wearing a ponytail and leggings, tennis shoes...

"She was sweet enough to ask me before the show. She was very sweet with my children and they had never been to a concert before and they were big fans and she said, 'Would you mind coming onstage during the song and dancing?' and I said to my children, 'What do you think?' - 'Oh mom, you have to do it...' and my youngest son said, 'Only do it if you want to mommy'. It was so sweet!"

Roberts fears it was a magic moment she'll never remember, adding, "It was one of those crazy out of body moments and I can't tell you anything that happened from the moment I came on stage, so surreal."