Walker was studying at New York City's prestigious Juilliard School, which forbids students from taking the stage until at least their junior year, when he became eager to test out some of his new material on a live audience.
The actor subsequently put his entire education on the line and secretly signed up for a one-night-only gig at nearby Gladys' Comedy Hole - but, the evening didn't go as he had hoped.
He tells The New York Times Magazine, ""I bombed, and thought I was going to die.""
A short while later a wide-eyed Walker accidentally let slip his experience during class and the 29 year old, who is married to Meryl Streep's actress daughter Mamie Gummer, confesses he was almost kicked out of the programme.
He explains, ""We were rehearsing and I said that a 'bit' (in my routine) wasn't working. My teacher was like, 'Bits? Shakespeare doesn't write bits. And how do you know what a bit is anyway?' I got a slap on the wrist for that.""
Walker is the star of upcoming movie Abraham Lincoln: Vampire Hunter.