"Madison Square Garden ... last show of the entire tour," Taylor teased. "That would seem like anyone's definition of a special occasion, don't you think? And on special occasions you want to be surrounded by your friends."
The country star went on to say that she and Selena had been best friends for four years, but never shared the stage together ... until now. The girls then launched into a duet of the 'When the Sun Goes Down' track in front of an overly excited crowd at MSG.
Watch their performance below. Do you think Taylor did the song justice? Should the two stars think about collaborating together again? Let us know your thoughts in the comments.