Musical comedy is genre enough. But add improv to the formula, and you have a potentially explosive brew -- if you’re lucky. This crowd is a find.

The six talented and largely loopy cast of the Loons come to audience in a ROYGBIV range of unprepossessing T-shirts and jeans, and flexibly dodge, leap, flit, and dart about the stage, drop down onto all fours and make like zombies or ragdolls, until you are giggling madly.

The trick with the Proverbials seems to be to select two random audience volunteers. The ones chosen to be mined for their life-stories when we were there seemed unpromising. One young male, black, was interested in media production, a just-graduated newbie from the Bronx who had a funny way about himself that looks promising for stage work after he finds his way in the world a bit. The second, a Little Ferry female who is also in media production, and wants to be a TV host, did not seem to offer much in the way of veins of improv gold to exploit.

But the troupe successfully reworked the spare factoids of these two folks, Brooke and Chris, into a skein of zany set pieces and hilarious comedic skits and gags.

Building on these two lightly experienced and initially unispiring subjects, the troupe developed songs, accompanying silly dances, and hilarious duo-partite ‘dialogs’ or blackout meditations that had us all laughing for the full hour.

Obviously the conventions of the form require that they have a few well-honed rough call-on pieces, modified by the evening’s selectees. Even for the cynical, seen-it-all theatre-goer, it’s hard not to have a bubbly and infective laugh-a-minute time. The evening we visited, there was a full audience; Joan Rivers had just died the day before. They incorporated encomiums to her several times throughout the performance. In a trice, they shift characters, voices, postures, facial tics, and expressions. No sets, costume changes or props needed.

Best news is that it may be one of the region’s biggest bargains. You can get tickets for $15 each, or, occasionally, twofers, even freebies, if you work their occasional ‘lottery’ correctly. Though it is only a bit more than an hour, it is a jolly way to initiate an evening, your insides are massaged by the nonstop laughter, and then you can  dine nearby and still get home before 10 pm.

First Saturday nights of the month seem to be a special. Weekends through the season and into the winter. They also produce a wide variety of socially conscious and experimental theatre and cultural enrichment programs for children and teens. They dispense comedy rewards the way Mother Theresa dispensed caritas to the lepers. Or something.

As we made our way to a local friendly eatery, a colleague of ours introduced us to a friend who has been an intern there backstage, and taking classes, for the past seven years. In theatre, that’s a hoary lifetime. They must be doing something right.

At the Castillo Theatre, 543 West 42nd St. Evenings at 8 pm.