Given the necessarily compressed nature of American Ballet Theatre's single week of performances at the Kennedy Center Opera House, the troupe still had a sizable store of novelties on tap for this past weekend. In the course of the Saturday matinee and evening programs, for example, we were treated to a new production, the return of former ABT principals, new repertory, new role assigments and new castings. Each program of the visit, in short, ended up with a share not only of expected pleasures, but also of adventure and risk.

The week's first account of Twyla Tharp's "Push Comes to Shove," created in 1976, found the ballet--with its head-on collision of vaudeville antics and fractured classicism--beginning to look like a period piece, though with no loss of its droll verve. In the limelight role made for him, Mikhail Baryshnikov gave a drily understated performance--as sly, nimble and mischievous as ever, but decidedly low-key. Elaine Kudo, Susan Jaffe and Cheryl Yeager were his deft female sidekicks, and as the second male lead, Clark Tippet, absent from ABT for some four years, made a fittingly lively return to the company in the zany role he was the first to dance.

Another company returnee was ballerina Gelsey Kirkland, one of the most sublime, extravagantly gifted dancers of our time, who has been slowly emerging from a period of great personal turmoil. She made a single appearance Saturday evening in a duet with Robert La Fosse in Lynne Taylor-Corbett's "Great Galloping Gottschalk." Her magnetism and lyrical intensity seemed untarnished and won her a personal ovation from a crowd obviously avid to welcome her back to the fold. Seeing her in this kitschy number was a bit like hearing Pablo Casals playing "Shortnin' Bread," but a gradual reentry into a more demanding schedule and repertory is no doubt the shrewdest course for Kirkland right now, to assure her an impregnable artistic recuperation.

What was billed as a new production of Balanchine's "Theme and Variations" consisted of newly designed costumes by Santo Loquasto and lighting by Thomas Skelton. Loquasto's embossed gray tutus suggest antique silver, an effect redoubled by illumination that seems to emanate from rosy-hued candles. Cynthia Harvey and Ross Stretton gave exceptionally fine, if not precisely consummate, performances as the principals in this demanding masterwork.

In their first time out in these roles, Magali Messac and Kevin McKenzie danced with apt nobility and refinement in the "Sylvia" pas de deux; also making role debuts were Deirdre Carberry and Gil Boggs (a new ABT recruit, formerly with the Atlanta Ballet) in a charmingly effervescent rendering of the "La Fille Mal Gardee" pas de deux. Among the new castings Saturday, the ones that made the most palpable interpretive impact were the ardent, assured and technically polished performances by Marianna Tcherkassky and Danilo Radojevic in the Shades Scene from "La Bayadere," during the matinee.