This town's standard pin-striped seriousness turned to whimsy last night.

Example: An affable fellow named Bill Krause shuffled through the National Communications Club wearing a cocktail napkin on his lapel with a duckbill platypus. "This is my platypus," said Krause, pointing to the emblem of WACPAC. "We chose platypuses--I never know what to call them, platypuses, platypusi--because we figure this is such a weird mix of people."

The mix was the 100-plus crowd that gathered for the WACPAC Founders' Day celebration, and Krause serves as the Whimsical Alternative Coalition Political Action Committee chairman. By day, he claims to be an important official at the AFL-CIO.

The WACPAC scene wasn't even warming up yet. It was finally political analyst Hodding Carter, the evening's master of ceremonies, rock singer Stephen Stills and a cabaret-type show that got the lawyers, lobbyists and government workers rolling.

"As we are reminded," said Carter, who was State Department spokesman in the Carter administration, "Democrats don't make great governors. Well, they don't make great comedians, either.

"When I asked this performer what to say about her when I introduced her, she said, 'I play around Richmond,' " said Carter. "I wasn't sure Washington would understand that."

The performer, political satirist/lyricist Diane Warren, an out-of-work teacher from Richmond, sang and poked fun at the presidency, including former presidents Ford and Nixon: "Well, here's your pardon, the one I promised you in the Rose Garden."

A parade of irreverent talent followed:

* "Rita Lavelle and the Shredettes" sang, "Met the man from Dow down at Lion D'or. Told him to clean his dump sites or he'd have to pay more. Say, 'Hey, hon, I'm the queen of the Superfund.' "

* Public Interest Follies representative Tracy Awsome filled in for congressional budget office chief Alice Rivlin and gave her Valley Girl interpretation of the federal budget: "I like looked at this budget, and said like, what is in this like, budget for me. Good job, president and like what a twink. Like what good are these mego missiles when, like, I'm like shopping at White Flint?"

* Keynote speaker Curt Donaldson, a Nebraskan carpenter who ran for Congress in 1982, unveiled his plan to bring the Soviet-American War Memorial to his hometown of Lincoln. To finance it, he said, he is selling high-temperature ceramic dog tags. "This happens to be dog tag No. 1. We made it for Ronald Reagan, and on the back his last line reads: 'Things Are Getting Better.' "

But because of cramped seating and long lags between acts, only a few fun-loving Washingtonians stuck it out to hear rock singer Stills.

Krause justified the evening's chaos, saying humor is the only salvation for Washington's driven. "People here are too serious. They work in it, they breathe in it, they eat it, they drink it."

It was also, he later noted, April Fools' Day.