Before Topher Grace became a household name as the lovably discomfited Eric on "That '70s Show," he was just another teenager looking for something to do. On the upcoming episode of MTV's "When I Was 17," the star of "Take Me Home Tonight" (which hits theaters next week) recalls his big break, which surprisingly stemmed from a turn in his high-school play.

"When I was 17, I made the varsity tennis team, and I wound up spraining my ankle twice, so I couldn't do that that spring," Grace mentions in the upcoming episode. The former athlete tried out for the lead role in his high school's production of "A Funny Thing Happened on the Way to the Forum," a part he didn't expect to land.

"I really didn't think I'd get it. There were some kids who were really great actors, and I still maintain that they were better actors then I am," Grace humbly notes.

Turns out, Topher's theatrical turn would change his life as he knew it. "So the crazy thing about that play is this girl who was a friend of mine -- her parents were big-time Hollywood producers. They wrote for 'Saturday Night Live,' they wrote 'Wayne's World' and 'Tommy Boy,' and they came up to me after the play and said, 'We'll call you at some point,' " Grace recalls.

But the actor misinterpreted the thrilling news, thinking he was being pursued to go on coffee runs instead of auditions. "I thought they needed a P.A. on one of their shows, so I said something really stupid."

Topher's pal Gordon remembered the error, too: "He was like, 'Yeah sure, baby. I'll have my people call your people.' "

Fast-forward nine months later, and the big-time producers had an opportunity for the actor that he almost couldn't believe. "They called me and they said, 'We're making a sitcom about the '70s.' I still thought they wanted an assistant, but they said, 'Oh no, we want you to audition.' "

Turns out this little sitcom just happened to be the massive hit that launched Grace's career.

Don't miss when Grace's "Take Me Home Tonight" co-stars Anna Farris and Dan Fogler dish on their adolescent occupations in the newest episode of "When I Was 17," premiering Saturday at 11 a.m. ET on MTV.