Carly Simon's classic 1972 confessional single "You're So Vain," which takes a self-absorbed mystery lover to task, could have served as the template for a good portion Taylor Swift's musical output thus far. Given that, it's only fitting that the two singers paired up for a rendition of that very tune on Saturday night.

"Before I bring out my special guest, I have this question that I've always, always had," Swift told the Foxborough, Massachusetts audience prior to Simon's entrance. "I think a lot of you have probably had this question too, always wondered what the answer is. Who is this song, 'You're So Vain' by Carly Simon, written about?"

Forgetting the fact that most of Swift's young fans have probably never wondered that, the duet is nevertheless a pretty good one, marred only somewhat by Swift's insistence on striking cheesy pin-up poses at every available opportunity. After the show Swift tweeted her elation at the opportunity to perform with Simon, writing: 

Check out the full performance in the video above and let us know what you think.