Shawn Mendes Sings Fall Tweets, Performs 'Mercy' on 'Fallon' (Video)

Shawn Mendes takes the stage while belting out his new ballad “Mercy” on The Tonight Show on Thursday (September 22) in New York City. The 18-year-old singer also had fun singing fall-themed parody lyrics to popular songs, submitted in the form of viewers’ tweets with the hashtag #FallSongs and read out loud by host Jimmy