San Jose Rep’s West Coast premiere of Theresa Rebeck’s rollicking three-person comedy The Understudy begins, like a track race, with a gunshot. The shot is fired from a prop pistol held by Harry, the titular understudy, who is goofing around in an empty theater while waiting for the rest of the cast and crew. Harry (Gabriel Marin) is unhappy about playing second fiddle to a big-name action movie star whose fame rests on lines like “Get in the truck!”

However, when said movie star appears in the form of Jake (Craig Marker), it becomes clear that he isn’t the hack Harry thinks he is. Jake takes the play (a production of an “undiscovered masterpiece” by Kafka) seriously and gives thoughtful insights into the author’s work, while Harry can only feebly reply that he went pub crawling in Prague once. Surprisingly, they get on well, and a significant “bromance” develops between them.

Harry’s relationship with stage manager Roxanne (Jessica Wortham) is more problematic. She is his ex-fiancée, and he abandoned her shortly before their wedding was to take place. This does little to facilitate the rehearsal, which turns out to be one headache after another.

In addition to conflict between the characters, there is an impressive rotating centerpiece for changing the scenery, which an unseen, stoned set technician continually causes to turn at the wrong time. This provides an opportunity for slapstick humor that never occurs, perhaps thankfully. The bantering between Marin and Marker, not to mention Wortham’s fits of flustered rage, are much funnier than any physical comedy.

Then there is the matter of the pistol. With such a realistic-looking prop in the hands of an actor with such a big chip on his shoulder, you can’t help but wonder if The Understudy might suddenly turn into a black comedy. The gun, however, is mainly a device for getting Roxanne off the stage when Jake misplaces it.

Though it asks its audience to suspend some disbelief, the play’s humor rings true. The actors, director Amy Glazer and indeed the whole crew must deal with frustrations similar to what the characters in the play go through. So too must have Rebeck, whose musical drama Smash covers similar ground. You get the feeling that years of disappointment and bitterness have been channeled into something positive: an engaging and hilarious comedy.

The Understudy
Run though June 3; $29–$75
San Jose Repertory Theatre, 101 Paseo de San Antonio, San Jose