Alexandrians in breeches and bodices shook off the 20th century yesterday and devoted themselves to their first and finest citizen, George Washington.

While many other Americans spent the weekend at store sales and in bargain basements, Virginians fanned out along the Potomac to celebrate the birth of the first U.S. president and Father of His Country.

"The man was a lion, and they look at us like we're circus animals," said Marguerite Chiarizia, who -- wrapped in an 18th century cape with wooden buttons -- helped reenact a Revolutionary War skirmish at Fort Ward. "Well, let them spend the day at shopping malls. This is no joke here."

In fact, Alexandrians appear to take nothing more seriously than the annual tribute to Washington, which culminates this afternoon with a parade through Old Town. On Saturday night, several hundred people draped themselves in 18th century garb and twirled to minuets, reels and the Colonial Cotillion at the city's annual Birthnight Banquet and Ball.

"This is our biggest weekend, and people are very religious about observing it," said Barbara Janney, director of the Alexandria Tourist Council. "The organizers really do feel they have a charge laid upon them."

Yesterday, in addition to the skirmish between the First Virginia Regiment of the Continental Line and His Majesty's 64th and 71st Regiment of Foot, visitors at Washington's favorite hangout -- Gadsby's Tavern -- were treated to a sample of the sights, sounds and culinary delights of Washington's time.

"Mom, this is disgusting, you have the rest," one boy yelped after knocking back half a glass of switchel, a popular 18th century drink made from molasses, vinegar and water.

The gingersnaps, one of the general's favorite snacks, went over a little better.

Gadsby's is one of the few remaining places that does not claim to have had the man as an overnight guest. He did, however, eat there when he was in town, and yesterday a magician and fencing partners demonstrated the way the general and his friends were entertained while eating.

Although nobody produced it, Gadsby's advertised Mr. Charles McKnight's "Learned Pig," apparently a big attraction in George's time because, according to contemporary descriptions, "the sagacity of this pig is equal, if not superior, to any animal ever exhibited in America."

As always, the stolid general himself hovered over the the events of the weekend. And while it is true that the original George Washington died in 1799, Alexandria lays claim to Richard B. Hills, arguably the next best thing.

"You look at a dollar bill and there's Dick Hills," said Michael J. McInerney, who will portray John Fitzgerald, Washington's aide-de-camp, in today's parade. "He's built like George, he walks like George, he's even let his hair grow the same way. The only problem is that he's two inches taller."

Alexandria's George Washington Birthday Celebration Committee says today's parade will be the largest to honor him in American history. More than 100,000 people are expected to turn out to watch a procession that has been planned for months and is costing nearly $100,000.

Anyone who questions the precision and thought that have gone into the planning of this year's parade should consult the comprehensive directions released last week: "All units will march at a pace of 112 28-inch steps per minute, and this pace will be set by Unit 8, Annex A, Order of March."

All participants, from George and Martha to the delegation from Bob's Big Boy Restaurant, are expected to comply.

Those who are determined to honor the general but who shy away from big parade crowds may tour his Mount Vernon estate today for free.

According to Christine Meadows, Mount Vernon's curator, Washington has been on a roll ever since the bicentennial in 1976. Last year more than a million people visited Mount Vernon, and Meadows expects to see even more visitors in 1985.

"You have the 200th anniversary of the Constitution in 1987, and 1989 marks the bicentennial of his inauguration," she said.

Visitors yesterday also were making the pilgrimage to the massive George Washington Masonic National Memorial, which houses within its forbidding walls George and Martha's family Bible, the silver trowel the general used to lay the cornerstone of the Capitol and a diorama with scenes from his life.

"Just look at that clock," said Sylvia Fried as she gazed at a timepiece that was stopped by his doctor the moment George Washington died. "Can you imagine it, the last time it ticked he was breathing."

Naturally, there is a philosophical dispute as to why Americans have continued so strongly to honor the man for more than 200 years, especially as Washington's critics contend he was icy and imperial, even penetratingly dull.

But his admirers have simply to tote up his accomplishments.

"He was the first president, he won the war, he founded the nation and he is our basic local hero," said Lilja Powell. "Let's face it, he has some great credentials."