Watching “Tour de Farce,” the newest production in the 30th-anniversary season at Penguin Rep in Stony Point, there are times when you might not believe your eyes.

The door-slamming farce – written by Philip LaZebnik and Kingsley Day and directed by James Glossman – stars Ames Adamson and Liz Zazzi, who change characters at the drop of a hat, sometimes by dropping a hat.

The speed at which they achieve the costume and character changes is dizzying. At times, there were gasps and murmurs of “How’d they do that?” from the Penguin Rep audience. One wonders if there isn’t an equally entertaining show going on backstage.

Director Glossman has plenty of tricks up his sleeve, from hidden exits to a team of backstage co-conspirators helping Adamson and Zazzi in and out of costume.

Over the course of a brisk two hours, Adamson plays a dimwitted bellhop, a clueless author, a philandering senator, a Swedish cameraman and a character we won’t reveal here.

Zazzi plays the clueless author’s embittered wife, a hard-charging telejournalist, a thieving maid, an ambitious hooker and a singing nun complete with accordion.

Don’t show up at the charming barn on Crickettown Road expecting Ibsen. Ibsen it ain’t. What it is is a thoroughly entertaining diversion for a late-summer night.

Set designer Ken Larson meets the key requirement of farce: The set has four doors to slam. Both actors make the most of the doors and their handful of characters, which are definitely a handful: They shift accents, change walks and slip from one perfect Patricia Doherty costume into another.

In the process, they fill the stage with believable characters who may have you convinced that there are 10 people in the cast.

Adamson’s exasperated author gets one of the night’s biggest laughs when he cries: “I want to take my shower. I’m getting tired of changing my clothes all the time.”

The backstage dressers are so vital to the success of “Tour de Farce” that they are brought out during a curtain call that is worth the price of admission. The dressers are Jillian Greenstein, Matt Hill, Linda Perez, Linda Rosen, and Andrew Trow.

Precisely choreographed down to the final note of the “William Tell” overture, the curtain call lets Adamson and Zazzi take their bows as each character – amid a breakneck flurry of changes.

Their final bows come in terry cloth robes, which look ideal for a rest.

They’ve earned it.

(Photo by Andrew Horn)