Show me 150 adults with scenes from Doonesbury comic strips taped to their backs and beers in hand, mingling for all they're worth, and I'll show you the victims of a Washington party game. As a rule, 30-year-olds who need party games in order to strike up conversations on Saturday night are better off reading a book.

Evenings choreographed on a theme, however, are a cut above the half-hearted artifice of party games. Theatrical ice-breakers on a given motif (medical/Hawaiian/Wild West/polyester), theme parties bring out the costumer and set designer in each of us.

Out-of-season themes give guests license to indulge in what would otherwise be clich,e. The beach scheme on Capitol Hill one dreary January evening, involving bare feet, hibachis and many 10-pound bags of white sand spread over the patio, was topped only by the upper Northwest cruise affair in February.

It was sleeting when the impromptu bash was launched. Portholes and a captain's wheel were watercolored and pinned to the walls, a plastic inflatable lifeboat strung from the ceiling and the roulette wheel set out. Guests made their way through the snow in mid-drift tops, cut-offs, sailor suits, Hawaiian shirts and sunglasses, and proceeded to spread beach towels under lamps, ask for Dramamine and play a tape of "Sea Cruise." Midway through the party, the captain announced a Port o' Call, dashed to the Safeway and returned with ad lib enchilada fixings.

But then, the days were short, the chill constant, and the idea of getting a suntan under a reading lamp seemed funny.

At a medical theme party, drinks were served in beakers, urine jars and strange vials. Guests wore intern, doctor, nurse and patient attire. An array of clamps, scissors, tongue-depressors and cotton swabs decorated the hors d'oeuvres tray. Some consultations turned into examinations, but that's another story.

The polyester bash featured a range of jumpsuits, pants suits, lime-green shifts, tacky ties and surreal jackets. Jewelry included "South of the Border" and "10 Commandments" charm bracelets and a dazzling array of plastics. The hostess wore screaming-yellow flood-length poly-pants and served Spam and Velveeta.

Dog parties have unleashed a stream of inventiveness. At one, four or five compatible canines celebrated the 14th birthday of a pal (that's 98 by human count; better not to wait for the milestone of 15). Milk Bone hors d'oeuvres, a doggie centerpiece and dog-food cake set the tone -- nothing as undignified as strapping party hats on these pets. At another, wet St. Bernard breath slobbered out the candles on a chocolate cake. The mutt of honor then lapped at the block of Neapolitan ice cream in his dish, sending it skidding across the linoleum. Separate eats were served the accompanying adults. (Hush puppies, perhaps?)

"Come as you were" was the rule for a reincarnation party that ended up in a hot tub on Seventh Street. The result was a couple of Egyptian princesses, a Druid or two, a priest in saffron robes and one grasshopper. Interestingly, no one pictured their former life as a GS-12.

Then there was the formal-dress Royal Wedding Party at 5 a.m. last July 29th, with tea, crumpets, champagne and a stand-in Queen Mother included. True believers in epaulets on pajamas, purple sash and tux, white gloves and bathrobes, and even a dime-store bridal veil gathered round the live-via-satellite fairy tale. For some it was a cynical joke, for others a documentary on wish-fulfillment.

An out-of-time favorite on the Forties theme is as close as I hope to get to V-J day. Sal Fiorito, a local artist with a flair for elaborate staging, was our host for "Club Fiorito," a throwback to a big-band ballroom held in an Adams- Morgan dance studio. An orchestra of cardboard cutouts on a raised bandstand was the backdrop for reels of Goodman, Basie and Ellington. A revolving mirrored ball covered the dance floor with specks of nostalgia. Neon art custom made for the occasion included a martini glass with an olive and the "club" logo, which was duplicated on the printed invitations and on the shades of tiny table lamps.

But the atmosphere relied mainly on the creative costuming of the guests.

Moues and mannerisms with cigarette holders were perfected in the course of the evening by women wearing hats with veils, platform heels, seamed hose, sequined gowns, red lipstick and gloves. Men in military uniforms, zoot suits or knickers, slicked hair, two-tone shoes and pencil- thin mustaches gave the Lindy their best hop.

All in all, it was a suitable backdrop for "New York, New York." Sal even enlisted a clean-up crew to restore the studio to the right timeframe before the next morning's dance class.

Clinically, role-playing may be frowned upon, but it's an easy way to face the music and dance.