Man and Woman are irreconcilably different animals. This fact throws a giant monkey wrench into the question of "intelligent" design, unless God also meant to fashion from Adam's rib the world's oldest running joke: creatures who are helplessly attracted yet are "endlessly crashing into each other like two vengeful bumper cars."

This is the tongue-in-cheek premise of I Love You, You're Perfect, Now Change, a wickedly endearing comedic romp through relationship heaven and hell. The bright-eyed and clear-voiced cast of the Northern Stage production sauntered through the silly sketches and saucy songs with winsome charm. Director Catherine Doherty's uncluttered staging let the four performers shine in this bracing bit of midwinter fun, as frothy -- and steamy -- as a hot cocoa spiked with Kahlua.

The show is a musical revue: The actors play multiple characters, with scenes linked by theme rather than by plot. Because it covers well-trod comedic ground, the production could easily have devolved into a superficial song-and-dance gloss on material stand-up comedians have been flogging for years. But razor-sharp lyrics put the cut in the humor, while some tender musical moments remind us that the need to love and be loved runs deep. Composer Jimmy Roberts and lyricist Joe DiPietro have clearly struck a chord: I Love You . . . is still running Off Broadway, nearly 10 years and 4000 performances after it premiered.

Act I covers the perils of the Single Life, as men and women fail to connect for reasons great and small. Time-pressed professionals on a first date consult their Palm Pilots -- and find it more efficient to skip ahead to breaking up. Awkward young lovers face crippling insecurities about tiny biceps and lumpy hips, wishing instead to be "A Stud and a Babe." Meanwhile, a middle-aged lout boasts: "My gut is expanding / In bed I'm commanding / By God, I'm outstanding / Why? 'Cause I'm a guy!"

By Act II, the fear of ending up alone has led Man and Woman "scared straight to the altar." But married life presents new opportunities for frustration and miscommunication. In trying to carve out time for passion, beleagured parents navigate an obstacle course as complex as a tango. "We played with Play-Doh and Nintendo / We watched Dumbo to the end, oh / Now it's time for fun that's rated X." Despite the headaches, a husband wonders about his bathrobe-clad wife, "Shouldn't I Be Less in Love With You?" and wistfully finds the answer is "No."

Kathryn Markey stood out as the ensemble's strongest performer for her supple, powerful singing and delicious comic timing. She made "Always a Bridesmaid" a hilarious highlight, boldly wearing a fuchsia-and-teal gown that looked left over from a Gone With the Wind-themed drag ball. She archly relished the song's outlandish rhymes, such as "taffeta / laugh at ya" and "velourish / whorish." In the "Marriage Tango," Markey proved inhibition-free as the horny housewife, strutting confidently in a red corset and orange boa (worn over a flannel shirt and sweats) and belting out the refrain: "I'm married, and I'm going to have sex!"

Chris Vaughn also showed great comedic and vocal range. He tangoed with goofy eagerness in a leopard-print thong (over khakis and a Dartmouth hockey shirt); made a convincing mussed-hair geek; conjured a shy tennis player unsure whether to bring wine or condoms to go with his date's lasagna; and played the world's sweatiest, most green-around-the-gills groom. He adapted his singing voice to fit the character of each song: raunchy and aggressive in "'Cause I'm a Guy," but soulful and tender in ". . . Less in Love With You."

Elena Gronlund and Frank Gayton sang with slightly less power and versatility than did Markey and Vaughn, but they created fresh and engaging characters. Both were delightfully disapproving as the disappointed parents in "Hey There, Single Guy." Gayton smoothly narrated a side-splitting commercial for "Jacoby & Meyers & Masters & Johnson," a law firm that redefines getting into bed with its clients. Gronlund gave an affecting take on a woman making her first dating video after a divorce that felt "like open-heart surgery without anesthesia." The sweet purity of her soprano made for a moving rendition of the show's memorable ballad, "I Will Be Loved Tonight."

The hardest-working performer, though, had to be music director Brett Schrier. He played the entire score from an onstage piano, accompanying every song and also playing seamlessly through every set change. Schrier demonstrated a thorough command of the show's music and supported the singers with sensitivity and verve.

This production makes a wonderful counterpart to last month's Guys and Dolls at Northern Stage. Fifty years after Frank Loesser's more wholesome, happily-ever-after musical was written, the onstage battle of the sexes in I Love You, You're Perfect, Now Change is a little less metaphoric and a lot more graphic. But the central issue remains the same: While Man and Woman may never fully understand each other, they are destined to keep up the chase.

The show opens and closes with the cast cloaked and hooded, chanting like monks -- just so we know, perhaps, Who is having the divine last laugh.