Lionel Stevens looked ordinary enough when he arrived with his junior high class at the Smithsonian's Spring Celebration yesterday, but he left with a different expression. As a clown turned Stevens' baseball cap backward and deftly applied bright daubs of greasepaint to his face, chaperone Janice Ricks called out, "You really don't need makeup, Lionel!" Stevens, 13, of Hampton, Va., mugged like a professional for the large crowd of onlookers when shown his transformation in a mirror.

A one-ring circus and a Wild West show alternated hourly under the outdoor big top at the free Spring Celebration, which continues today and tomorrow, from noon to 5 p.m., at the National Museum of American History. Inside, there is a circus sideshow (with a tattooed lady, an ancient Hawaiian hula act and a sword swallower), circus craft workshops and more than a dozen short films on the circus art and heritage.

Backstage at the circus:

"We build fantasy characters: from the bead on the top of the hat to the wig and the flower on the lapel and on down. By the time I'm finished with you--you're not you," said clown outfitter A.J. Fast. A gaggle of gawkers moved back as a visitor strode toward them in a pair of Fast's 32-inch, red-and-white diamond patterned shoes (size 10 1/2), "the longest shoes in the world," according to Fast, who has been a clown for 32 years.

The yellow-and-white striped circus tent was packed, so some kids perpetuated a time-honored tradition and crawled in under the canvas flaps. Others stood outside listening to the shrill calliope. Inside the tent, Mary Ruth Herriott, housecoat over her sparkling costume, frantically brushed her huge performing poodles and snapped on their blue rhinestone collars minutes before being whistled into the ring by her husband, ringmaster John Herriott. Behind her, acrobat Krystina Knop balanced on one toe atop husband Chris' forehead.

At the indoor sideshow, sword swallower Jack Bradburn polished off a two-foot saber. "And that was one of the easy ones," Bradburn said, before he popped two antique blades down his throat. "I've been a fire-eater since I was 14," Bradburn said. "One day my boss needed a sword swallower, so I learned to swallow three swords in one day. Back then, $150 a week was a lot of money".