The dapper leopard in spotted fur mask, ascot, corduroy jacket and boots, lit up a cigarette and introduced himself."We're aliens from outer space," he said, as his friend, also in fur head mask, fur cape and satin top nodded agreement.

Actually, he looked quite at home in the Corcoran Gallery Saturday night as he took in the scene around him -- a Pez dispenser sipping a can of beer; a very large nose with his girlfriend leading him around by the arm; two white-skinned, blackclothed figures with matching drops of blood on their necks searching the room for the organizer of all this seeming madness.

The occasion was the Beaux Arts Masquerade Party, a fund-raiser for the Corcoran School of Art, a radical departure from the Corcoran's other annual affair -- the sedate white-tie Corcoran Ball. Still, one guest, neither student nor a regular social-circuit worker, said the party was what he would expect of the Corcoran students and cohorts -- "very Bohemian."

By 11 p.m. the gallery's austere gray-walled rooms were filled with costumed folk. White face, green face, black face, blue face. Half white, half black. Face paint was very popular, as if dozens of the ball participants had suddenly decided that afternoon, either out of last minute desperation or excited inspiration, that face paint made the ultimate sensational costume.

Not that this ball was anything like the Arts Ball thrown by Parisian art students every June in the '20s, where complete body paint was typical for loin-cloth-clad men and bare-breasted women who spent all night in notorious Bacchanalia.

At the Corcoran, there was Spiderman, alias Stan Fowler, a graduate student in chemistry at Catholic University, who had cut, dyed and sewn together the pieces of his "milliskin unitard" to get the Spiderman look of bright blue and red from head ot toe.Black lines of webbing were expertly sketched across the fabric covering his face and torso.

"I saved the Sunday comics for a month to see Spiderman and how he puts his webbing on," Fowier said casually, talking through the fabric over his face. "But each week this guy Stan Lee changed the stripe patterns so I couldn't tell what to do."

Fowler as Spiderman enterd a costume contest at anothe masquerade ball in Washington around Halloween, but he lost to someone dressed up as a box of McDonald's French fries. "The french fries were with this gorgeous-looking hamburger and they won as a pair," Fowier said. "But Spiddeman's a loner."

There were so many loners at this masquerade party: Corcoran student Michael Hogan dressed in a heavy brown cape and had a square mirror over his face. The costume so delighted his friends that they squealed and bestowed lavish kisses upon his mirror. "I gurss I'm every man," said Hogan in muffled voice.

The crowd was hardly wild; many of the masquers were constrained by the costumes they wore. Sam Verts, a local designer dressed as the Washington Monument painted with a pattern of stars and stripes, was led through the party slowly by his friend Bob Olmstead, a sculptor.

"This is the only party I've been to in Washington where people aren't social climbing," said Mary Jo Campbell, there with her husband Doug; they were social chairmen for the International Horse Show this year. They wore formal clothes and masks, which they frequently took off, saying, "It's so refreshing."

Doug Campbell said this was not the place where most of Washington's social set would be. "They're very safe," he said. "This is very avantgarde for Washington."

Or boring for others. "The theme of this is self-indulgence," said artist Claudio Eskenazi, a veteran of masquerade balls in Brazil and Paris.

"In the old days, there was a sense of shared indulgence, where you did things together," he said. "Here there're too many weirdos. There's nothing wrong with weirdos, but if they are weirdos whom you don't know, that's different."

Adolph Lawrence, a second-year student at the Corcoran school, won the best costume award, a nine-day trip to Europe. He was dressed to look like a man hanging upside down from a tree limb.

Peter Marzio, director of the Corcoran Gallery, said the ball would probably be held again next year. "This kind of thing isn't done often in Washington and if people enjoy it that's good.

"The important thing that tonight shows is the unity of the gallery and the school," he said.