"Don Quixote," which the American Ballet Theatre danced at Kennedy Center all weekend, is not a work that differs drastically depending on cast. It remains immutably a lark, changed neither by passionate nor playful performances.

The leading man's part of Basil the Barber was re-choreographed by Mikhail Baryshnikov with himself in mind. Danilo Radojevic resembled Baryshnikov more in body type and energy production on Saturday afternoon than did Kevin McKenzie in the evening performance.

Radojevic is compact and dynamic. His corkscrews and other Baryshnikov fillips were emphatic, as intended. If the results looked only athletic, it was because he never relaxed into a movement in order to shape it as dancing. His characterization of Basil was simply high-spirited.

McKenzie, streamlined by nature and delivering sustained movement rather than explosive power, was astute in adapting steps to display his long line. When that wasn't possible, he diminished the scale of a phrase. On occasion, he'd waver. The singularity of his performance, though, was in the realm of the feelings. Basil, in McKenzie's impersonation, became a romantic hero whose savoir-faire was merely a social mask. This role is a substantial addition to the dancer's other original characterizations that have been known to change the look of some ballets, like Roland Petit's "Carmen" last week.

Marianna Tcherkassky, as the desired innkeeper's daughter, Kitri, dashed on at the matinee like a spitfire. Yet her purist's reputation remained intact with clear footwork and careful attention to hands and arms. She almost managed to keep Kitri's movement forceful throughout the three acts.

Cynthia Harvey, McKenzie's Kitri, is now so sure of the role's technical hurdles that she could afford to remedy a movement quality which, in Act 1, threatened to become leathery. Brusqueness may be part of her conception of the character, but the attendant busyness seemed superfluous.

In the afternoon, Amour was danced with truly gentle charm by Deirdre Carberry; at night Christine Spizzo added a wicked sparkle. Nancy Raffa, new to ABT, was one of Kitri's bosom friends Saturday night. Her elegant Ballet Russe bearing in the corps has commanded attention throughout this run. When spotlighted, Raffa was pressed for time and even took a spill but still seemed special. There were good renditions of Mercedes as street dancer and Mercedes as dream figure by, respectively, Lise Houlton (evening) and Lisa de Ribere (matinee). Leslie Browne alternated with them, dancing both halves with dogged determination. When these roles were first merged into one character under Baryshnikov's direction, there seemed to be some dramatic sense behind the decision. Now that two dancers share the "one" part at each performance, the audience is puzzled.

Sunday evening's "Don Quixote," with much the ssme ABT cast as the previous night, scored notches higher in exuberance and accomp-lishment. 'Cynthia Harvey's dancing had mellowed. There was not a misstep on Kevin McKenzie's part. Nancy Raffa caught the pace and kept it with ease. Paul Connelly's conducting breathed with humor and bravura.