Alexander Calder (1898-1976) spent his life in play. As a child, as a youth, even as an old man, he loved circuses and zoos, movement and bright colors, gadgets, puns, and toys. No sculptor of our century has poured into his work -- or given to his public -- more undiluted fun.

"Calder's Universe," his joyous retrospective which goes on view today at the Hirshhorn Museum and Sculpture Garden, is as full of sweet surprises as any Christmas morning. Soar with Calder's mobiles, gambol with his kittens, giggle with his clowns. He liked dressing in red flannel. He was white-haired and big-bellied. Had he worn a beard, Calder, in his workshop, would have looked like Santa Calus.

He was, the scholars tell us, historically important, the inventor of the mobile and a founding father of kinetic art. Where would rational George Rickey or galumphing Mark di Suvero be without his example? Calder knew Mondrian, Matisse, Miro, and Giacometti. He understood the masters, but his work was not like theirs.

He grew up in the art world. His father was a sculptor as was his grandfather, Alexander Milne Calder (1846-1923), who worked for more than 20 years on the 37-foot-high statue of William Penn that looks over Philadelphia from the tower of City Hall.

There are other worlds like Calder's -- one thinks of Never-Never Land, of the Big Rock Candy Mountain, and the nicer parts of Oz -- but more of them are found in the literature of childhood than in the realms of art.

Calder's retrospective opens with the free, amusing drawings of porcupines and pelicans and other curious creatures he sketched at the zoo in 1924. His stabile "Flamingo" of 1974 is as humorous and gawky as the birds he'd drawn from life half a century before.

He drew animals and painted them, bent them out of wire and snipped them out of coffee tins. He was fond of curly-tailed pigs, bulls and prancing hourses.No matter what his subject or material, Calder's exuberance shines through.

His largest public sculptures are by now so familiar -- there are scores of them displayed in shopping centers, office buildings, airports and museums -- that they've begun to seem a little bit cliched. But his smaller, wholly handmade works have lost none of their freshness. Look, for instance, at his salad forks and ladles, his "Double Cat" (carved from a log in 1930), his stage props and pull-toys.

His art is almost never stern. His "Roxbury Flurry," a mobile of 1948, suggests a child's joy at a New England snowstorm. Even his abstractions, for instance "Wooden Bottle With Hairs," tend to make us laugh.

Despite the stolid portraits of the 18th century, and the stuffed-shirt statues ground out in the 19th, fun has never been absent from our art. Think of circus wagons, tavern signs, cartoons, and Norman Rockwell's covers. Calder somehow managed to bring that fun, that playfulness, in modernist high art.

The Hirshhorn's exhibition is a smaller, traveling version of the Calder retrospective that opened in Manhattan at the Whitney Museum of American Art in 1976. The present exhibition has been beautifully installed by Joe Shannon of the Hirshhorn. Though only half as big as the Whitney show, it well may be nicer. For fun ceases to be fun when there is too much of it. This version is a treat. Never does it pall. "Calder's Universe" closes May 13.