Thomas James Jagodowski tries not to worry his parents. So when the mystery symptoms he’d been experiencing for months—the dizziness, the loss of coordination, the confusion, the constant sense of rocking back and forth—got especially bad one evening in the summer of 2000, he didn’t call them. A fixture of Chicago’s comedy community, Jagodowski has plenty of close friends, but he didn’t call any of them; everyone he could think of was performing in a show somewhere. And he didn’t call 911 either. Instead he grabbed his wallet, so his body could be identified, and went out to the sidewalk, where he waited to die. “I stood on the corner of Hamilton and Addison for half an hour and I didn’t die,” he says. “So I went to go rent a movie.”

But as well as he’s learned to manage the mysterious affliction, it hasn’t gone away. And in certain situations, it can produce a smothering anxiety that’s far harder on Jagodowski than regular stage fright. Oddly, improv doesn’t bring it on—but scripted material does. So though he’d like to do plays, he says, “I end up asking my agent for one-line parts or things that don’t have talking in them,” or for special situations such as Stranger Than Fiction, in which he was allowed to improvise his performance. Otherwise, most stage and film work is out.

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Jagodowski grew up in Holyoke, Massachusetts, the oldest son of a plumber and a grammar school teacher. There were no performers in his family. Instead, he says, “we have ski shop owners and old soldiers.” His only early brush with the stage came in eighth grade, when he was cast in a musical at his Catholic school. “I had one rehearsal with the lady who was supposed to play piano,” he says. “They didn’t say this, but I know this is true—I was so bad they canceled the whole thing. Then our high school didn’t have plays, so I didn’t really think about it.”

But the low point of his college career had nothing to do with academics. It had to do with a vending machine. “I went to buy some Munchos, and it didn’t give me my Munchos,” he says. “So I went around to the back of the machine and kind of jostled it. It started to fall. It made total sense at the time to think ‘Boy, that’s going to be loud. I better catch it.’” The machine landed on his leg, which—when he extricated himself and tried to stand up—made a noise “like a sock full of billiard balls.” His tibia and fibula were broken and bone pierced his skin. “I got a couple of plates and a bunch of screws put in, the whole shebang,” he says. Later staph set in, and he came close to losing the leg. It’s a story he’s shared onstage during the monologue-driven Armando Diaz Experience show at iO.

If Jagodowski’s college follies hadn’t killed off his inner salutatorian, improv training did its best to finish the job. He quickly learned that left-brain thinking gets you nowhere in improv. “It was the first time I heard the word ‘clever’ used as an insult,” he says. “The whole thing is, in a weird way, to be OK with being unprepared. If you can get to the point where you can realize that the moment is going to take care of you, and that your thinking is only going to get in the way of that, then you’re going to be fine.” That moment-to-moment approach spilled over into his life offstage. “I didn’t really think about how it was supposed to work out, or about making a living at it,” he says. “I just knew that that was the best three hours of the week.”

For a couple weeks he tried to continue performing. One night he went onstage only to blank out in the middle of a scene. He didn’t know what to do except walk off. “I looked at the running order [of the show’s scenes] and didn’t recognize a single thing on it. If it had said Richard III I would have gone, ‘OK, I don’t know any of the words to that either.’” Each night McBrayer, his understudy, waited with him in the wings until showtime, when Jagodowski would decide if he could go on or not. “It was an awful thing to do to a cast,” Jagodowski says. “If they can’t rely on you to do your stuff, then you can’t stick around.” He quit. He tried again in 2001, with a brief return to Second City’s lower-profile E.T.C. stage, but once more had to leave before the show’s run ended.

In the end, after all the doctor visits, Jagodowski decided that all he could do was get used to the disorientation and avoid whatever made it worse—including scripted material. In improv, not only can he invent a reason for his character to sit down or walk offstage if he feels woozy, but he has to be so engaged and present that there’s no room for anxiety to blossom. With scripted material, his mind has more space to freak out in. He did force himself to accept a small part in the 2005 John Cusack vehicle The Ice Harvest, directed by Harold Ramis. “Everybody on it could not have been cooler or more pleasant,” he says. “Mr. Ramis could not have been nicer or better at what he does. And I absolutely hated it. It was a terrifying experience.”

At the Chicago Improv Festival, Sat 6/7, 10:30 PM, Lakeshore Theater, 3175 N. Broadway, 773-472-3492 or chicagoimprovfestival.org, $25.

TJ Jagodowski With Chicagoland

Open run: Tue 8 PM, Annoyance Theatre, 4830 N. Broadway, 773-561-4665 or annoyanceproductions.com, $8.