Matt Damon’s portrayal of a brilliant MIT janitor in Good Will Hunting propelled him to stardom in 1997. So when he delivered this year’s commencement address, it was a homecoming of sorts, and he willingly posed for a selfie with senior class president Anish Punjabi ’16 and vice president Nicole Effenberger ’16. Damon, who founded Water.org to help provide clean water to the millions who lack it, urged MIT grads to tackle the world’s big challenges—and to keep learning. “Today’s not the day you switch from ‘receive’ to ‘transmit,’” he said. He also joked that it was his second “fake” graduation: he wasn’t given a diploma at his Harvard commencement, having left a semester early to pursue acting. But he didn’t leave MIT empty-handed: in a nod to his role as a “space pirate” in The Martian, he received an honorary MIT Pirate Certificate.