Donald O'Connor, the rubber-limbed song-and-dance man best known for his starring role in ''Singin' in the Rain,'' died Saturday at age 78, his family announced. In frail health for several years, he succumbed to heart failure at a retirement home in Calabasas, Calif., daughter Alicia O'Connor told the Associated Press.
Born to circus performers, O'Connor had a career that spanned more than seven decades, performing in vaudeville as a child and breaking into the movies at age 11. He first found adult fame in the early 1950s as the star of the six ''Francis the Talking Mule'' films (a precursor to TV's ''Mr. Ed''), quitting the franchise after jokingly complaining that the mule got more fan mail than he did. He won an Emmy as a guest host on ''The Colgate Comedy Hour'' in 1954 and soon hosted his own variety show. After the success of ''Singin''' (1952), in which he played Gene Kelly's wisecracking sidekick Cosmo Brown, he starred in other movie musicals, including ''Call Me Madam,'' ''There's No Business Like Show Business,'' and ''Anything Goes.''
In his later years, O'Connor turned up occasionally in cameos on TV (''Tales from the Crypt,'' ''Frasier,'' ''The Nanny'') and in movies, where he played Robin Williams' father in ''Toys'' (1992) and proved he still had some dance moves at 72 opposite Jack Lemmon and Walter Matthau in ''Out to Sea'' (1997). Always, however, he was best remembered for ''Singin','' especially his show-stopping ''Make 'Em Laugh'' song, an encyclopedia of acrobatic pratfalls distilled into one musical number. ''Make 'Em Laugh'' remained O'Connor's credo until the end; according to his family, among his last words were, ''I'd like to thank the Academy for my lifetime achievement award that I will eventually get.''