The singer — dressed in the same suit as Fallon — first popped up during the opening monologue, with the two co-hosts setting up each other’s punchlines.
After taking part in Fallon’s ritual Thank You Notes segment and an outfit change, the co-hosts played a game where they smashed eggs against their heads, not knowing whether they were raw or hard-boiled. After getting yolked on his attempt, Mendes won the game by pulling hard-boiled eggs for the rest of his turns:
With Mendes behind the desk along with Fallon, the duo next chatted with Modern Family star Jesse Tyler Ferguson before the singer served as interviewee and interviewer, switching plans with Fallon during the segment:
Mendes capped off his hosting duties with a performance of his latest single “When You’re Gone,” a breakup song he previously debuted at SXSW: