By Meghan Overdeep
Sep 15, 2015 @ 9:00 am
Michael Loccisano/Getty

Julia Roberts has finally spilled on what it was like to dance with Taylor Swift on stage.

On Aug. 15 Swift invited the Oscar-winner and Joan Baez to come out onto the stage during her performance of "Style" at Levi's Stadium in Santa Clara, Calif.

"It was one of those crazy out-of-body moments—I can't tell you anything that happened from the moment I came on stage. "I was so nervous!" Roberts told Extra.

The actress confirmed that the surprise appearance was hardly planned. "I would have washed my hair. I was, like, wearing a ponytail and leggings, tennis shoes ..." the 47-year-old mother of three jokes. "No, she was sweet enough to ask me before the show."

Turns out it was her kids, 8-year-old Henry and 10-year-old twins Phinnaeus and Hazel, who convinced their A-lister mom to hit the stage with the "Blank Space" singer (and 2015 InStyle Social Media Awards nominee—vote for Swift here).

Tonight Joan Baez and Julia Roberts danced it out to 'Style'. These two women are my heroes. What an honor.

A photo posted by Taylor Swift (@taylorswift) on

"[Swift] 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!' " she says they told her. "And my youngest son said, 'Only do it if you want to, Mommy,'" recalls Roberts. "It was so sweet."

Not bad for their first concert!