Tavi Gevinson began performances on August 18 in This Is Our Youth, starring opposite Michael Cera and Kieran Culkin. “It went really well, I think,” the 18-year-old modestly told Jimmy Fallon on The Tonight Show the next day. The teenage founder of fashion website Rookie, whose words escaped her when trying to describe the experience of making her Great White Way debut (it’s much easier to use abstract motions), discussed what goes on backstage at the Cort Theatre: lots and lots of Mario Kart, N64 style. The ‘90s pastime is a decade shy of when the Kenneth Lonergan play takes place, but it's certainly more innocent than what their characters go through on stage. Take a look at the interview below, then catch Gevinson in This Is Our Youth, now in previews!