It seems like a dubious musical mash-up: Broadway narcissists-turned-activists take over a middle-American town to help a lesbian teen who just wants to bring her date to the prom. But with a tuneful score, a playful book, and performances that remind you what Broadway heart and chutzpah are all about, this cause celebre of a show turns out to be a joyous, funny, and sweet production that should appeal to several generations of musical fans.

Bob Martin (“The Drowsy Chaperone”) and Chad Beguelin (“Aladdin”) wrote the lively, tender, big-laugh book — based on an original concept by Jack Viertel — for the musical that premiered at Atlanta’s Alliance Theater two years ago. It’s a 21st century “Bye Bye Birdie,” with showbiz interlopers causing havoc before finding their better selves — but re-imagined with a millennial slant and an echo of “Dear Evan Hansen” empowerment.

Leading this desperate group of career-slumping Rialto hams is Dee Dee (Beth Leavel, in a deliciously grand performance), who brandishes not just one but two Tonys to get a motel room upgrade. “How do you silence a woman who’s known for her belt?” declaims this diva, rhetorically, and pity those who would try.

Then there’s her co-star in their just-flopped musical “Eleanor,” Barry (Brooks Ashmanskas), who declares, “I’m as gay as a bucket of wigs,” and proves it by practically levitating out of his loafers.

Rounding out the quartet is the always-the-standby Angie (Angie Schworer) who shows she can still get a leg up on life, and Trent (Christopher Sieber), a clueless Juilliard actor/waiter whose non-Equity “Godspell” gig just happens to be bus-and-trucking near the problematic prom. Also along for the ride is long-suffering publicist Sheldon (Josh Lamon), who might not deliver Jimmy Fallon but can book a gig at the monster truck rally.

|CONTINUED|