The Insider.com

Taylor Swift played the final show of her Speak Now tour at Madison Square Garden last night, and in Taylor's own words, what better way to do it than with your best friend?

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To deafening screams of teenage delight, Selena Gomez surprised the full house, joining her pal in a duet of Who Says.

Believe it or not, this is the very first time the two have shared a song onstage. Aww.

The video is best around the 1:55 mark.

MORE: Justin and Taylor's Surprise Duet