Nov. 7 (Bloomberg) -- Playwright Theresa Rebeck has described her off-Broadway dark comedy “The Understudy” as a love letter to the theater. Mark-Paul Gosselaar, a television actor with no prior stage experience, is an unlikely messenger.

In the play, Gosselaar plays action star Jake, rehearsing a newly discovered “masterpiece” by Franz Kafka. Opposite him is Harry, a struggling but gifted stage actor (Justin Kirk), hired as an understudy.

The comedy skewers the upside-down world of Broadway -- where inept film stars may land plum roles and gifted stage actors are lucky to find work as their understudies. Director Scott Ellis said he hired Gosselaar with some trepidation even though the actor had aced a Los Angeles audition.

“You always take a risk with someone who doesn’t do stage; there are so many ways it can go wrong,” Ellis said in a telephone interview. “It’s wonderful to watch someone embrace it and be good at it.”

Gosselaar became famous as a blond teenager in the situation comedy “Saved by the Bell,” which aired from 1989 to 1993. He’s now a rumpled public defender on “Raising the Bar,” a legal drama that airs on TNT.

The actor said he was eager for a new challenge after shooting the second season of “Raising the Bar.”

“I didn’t want to be sitting around,” he said in an interview at the Laura Pels Theater, home of the Roundabout production. “I told my agent, ‘I don’t want to wait to see if the series is picked up. Put me to work.’”

Pursue Theater

His new agent at Paradigm Talent Agency, Chris Schmidt, suggested he pursue theater.

“This was exactly what I was looking for,” he said.

Early in “The Understudy,” Jake boasts that stars bring “visibility and shall we say ‘excitement’” to Broadway and belittles Harry, the reserve actor. So does the stage manager, played by Julie White.

“You have no rights,” she tells Harry, who jilted her on their way to the altar. “Jake is a movie star. That means he is the crown prince of the universe.”

Gosselaar, a competitive cyclist, bulked up his six-foot frame to play Jake, doing as many as 40 pull-ups in his dressing room a day.

“As an action star, Jake has a trainer. Jake is very aware of his appearance,” said Gosselaar. On “Raising the Bar,” he does the opposite, skipping gym and eating whatever he wants.

The biggest difference between TV and stage? The rehearsals. Gosselaar said he was surprised by the depth of stage rehearsals, recalling the hours sitting around a table, exploring the text and characters. In TV, he said, these warm- ups are as much for the crew as the actors.

“I’d never given a performance until the red light is on,” he said. When rehearsing for stage, “I felt so exposed.”

Gosselaar said he’s energized by his New York sojourn.

“I didn’t want to stand still,” he said. “I’m young; now’s the time to take chances.”

To contact the writer on this story: Philip Boroff in New York at pboroff@bloomberg.net.

Last Updated: November 7, 2009 00:01 EST