'The World's Best' - Ariana Grande Surprises TNT Boys "And i'm telling you" Reaction

After James Corden interviews the TNT Boys about their experience on 'The World's Best' and their love of Ariana Grande's music, the boy band starts performing "And I Am Telling You I'm Not Going." Midway through, Ariana Grande surprises them by walking onstage and finishing the song with them.