Taylor Swift Brings Carly Simon On Stage To Sing 'You're So Vain' (VIDEO, PHOTOS)

Long before a boy ever broke Taylor Swift's heart, Carly Simon was the one refusing to name the names that inspired her chart-topping hits about former flames who wronged her so.

It shouldn't shock anyone to learn that Swift is a huge fan of Simon, and it makes sense that the legendary singer would join Swift on stage as surprise guest at the Foxborough, Mass. stop on her "Red" tour at Gillette Stadium on Saturday night.

Just as Swift remains coy about who her own songs are written about, so does Simon, who has yet to reveal who her 1974 hit "You're So Vain," was inspired by.

Singing with Simon was a dream come true for Swift, who tweeted about the experience after the show:

CORRECTION: An earlier version of this article stated that Carly Simon identified David Geffen as the inspiration behind "You're So Vain." Simon refuted this on her website, claiming the rumor was made up by a British tabloid. To this day, Simon has yet to reveal who the song was written about.