On Saturday night Taylor Swift took the stage with Carly Simon to perform "You're so Vain" in Foxborough, Massachusetts. Of course the performance had people buzzing but more so about who and what inspired Swift to perform the classic break up song.

While at the Gillette Stadium the duo performed the 1972 hit, "Every girl out there will be thinking of someone when we're singing," Swift told MTV while backstage before the two belted out the classic song.

According to E! News, while discussing how excited she was to be performing the hit song with Simon the "Red" singer said, "When I heard 'You're So Vain' I just thought, That's the best song that's ever been written."

"That is the most direct way anyone has ever addressed a breakup. It's amazing."

"It's a song that really sort of developed that style of mine," Simon added.

"And a lot of it was not knowing that I was developing that style, 'cause a lot of things happen by accident, don't you feel?"

"Yeah," Swift agreed, "especially with songwriting."

Before bringing out the singer on stage Swift teased the crowd and said, "Before I bring out my special guest, I have this question that I always, always had, and I think of you you have probably had this question, too, and wondered what the answer is."

"Who is the song 'You're So Vain' by Carly Simon written about?" The singer pondered the thought before flipping her ponytail over her shoulder and saying, "As if." The blonde country cutie wore a fitted black and white striped t-shirt with red high-wasted shorts.

Who do you think Taylor Swift secretly dedicated the song to? She has a long list of exes including Harry Styles, John Mayer, and Connor Kennedy to name a few. What is your vote? Leave us a comment below.