“Denver, Denver, I’m from Denver.” With those five words, comedian T.J. Miller created the summer rap hit of 2012, in Denver at least. Featuring quintessential scenes from the Mile High City, including Colfax Avenue and Casa Bonita, the facetious music video became an instant YouTube hit, eventually serving as an ad for his critically acclaimed Mash Up series on Comedy Central. But the East High School alum won’t be a household name just in Colorado for long, thanks to a slew of big (and small) screen roles this summer: He acts opposite Mark Wahlberg in Transformers: Age of Extinction, is the voice of Tuffnut Thorston in How to Train Your Dragon 2, and stars in the comedy Search Party.

These breakout performances almost never happened, though. At 28, Miller nearly succumbed to the ultimate curtain call when he was diagnosed with a cerebral arteriovenous malformation, a dangerous tangle of veins and arteries in the brain that can induce hemorrhaging, seizures, and hallucinations. In 2010, while filming Yogi Bear in the New Zealand forest, Miller, now 32, began behaving oddly, involuntarily narrating things as he was doing them. After successful brain surgery, Miller says he emerged stronger and funnier than ever—in part because his near-death experience taught him not to take life too seriously. “Life is this ephemeral, ridiculous thing that could end at any moment,” he says. “Don’t hesitate to laugh at any part of it.”

Miller discovered his knack for making people laugh during drama class (and as the class clown) at East High then upped his game with a global education in humor. After graduation, he studied Shakespeare at the renowned British American Drama Academy in Oxford, England; circus arts in Paris; and improv at Annoyance Theatre in Chicago. His big break came in 2007, when he gained a following with a recurring role on ABC’s Carpoolers. The following year, Miller made his feature film debut in J.J. Abrams’ sci-fi monster smash, Cloverfield. He started making the rounds on Comedy Central, Chelsea Lately, and the Nerdist Network’s Cashing In with T.J. Miller. Feature film credits racked up: How to Train Your Dragon, She’s Out of My League, Get Him to the Greek, Unstoppable, and Our Idiot Brother. “To this day, I do not consider myself a good actor,” he says, just a busy one.

Although Miller now lives in Los Angeles, his humor—and his heart—never stray too far from home. “My drama teacher at East, Melody Duggan, is the whole reason for my success,” he says. “I remember her saying, ‘None of you will ever become comedians—except for T.J.’ I thought, I guess that could be an option.”