During his heyday in films, in the 1930s, Mr. Rooney was known for his seemingly limitless exuberance, an effervescent, nearly hyperactive screen presence who seemed preternaturally inclined to entertain.

He was best known for the popular series of Andy Hardy films, beginning with "A Family Affair," in which he embodied American optimism as the son of a small-town judge; and for a series of peppy musicals—notably "Babes in Arms"—where he and Judy Garland would inevitably put on a fund-raising show as the solution to some mounting problem. Other significant movies of this period, in which he got to display his acting chops, included Max Reinhardt's famous film version of "A Midsummer Night's Dream" (1935), where he played Puck, and "Boy Town" (1938), with Spencer Tracy.

Though frequently accused by critics as being manic and hammy, audiences loved the 5-foot-2 dynamo. He was a top box-office draw for many years, all while still being a teenager. In 1939, America’s theatre owners voted Mr. Rooney the No. 1 box-office star. That same year, he was given a special Academy Award “for bringing to the screen the spirit and personification of youth.”

The following year, he became the first teenager to ever be nominated for an Oscar, for "Babes in Arms." He was even lucky in love, marrying Ava Gardner, arguably the most desirable starlet in Hollywood at that time, in 1942. The union would last a year. It would the first of Mr. Rooney's eight marriages.

Following one of his most famous turns, in 1944's "National Velvet," opposite a young Elizabeth Taylor, Mr. Rooney enlisted in the armed forces, entertaining the troops and working on the American Armed Forces Network. When he returned, he resumed work. He was nominated for Oscars for "The Human Comedy" (1944) and "The Bold and the Brave" (1957), but found the transition from eternal youth to mature leading man difficult. His short stature and boyish face didn't help matters. "I was a 14-year-old boy for 30 years," he would later observe. By the time he was in his 40s, he was bankrupt and nearly forgotten. (Addictions to gambling and horse-racing, as well as numerous claims for alimony and child support, forever dogged his finances.) Though he never stopped working, his career from then on became, to a certain extent, a series of comebacks. He won critical praise for his performance as a down-on-his-luck trainer in the 1979 horse drama "The Black Stallion." The part won him an Oscar nomination.

His most celebrated, and unexpected, comeback, however, came on the stage. In 1979 he made his Broadway debut aside Ann Miller in Sugar Babies, a bawdy, proudly old-fashioned burlesque revue in which Mr. Rooney, with undimmed vivacity, provided nearly all of the comic relief. The show was a smash. It ran for years, and was nominated for nine Tony Awards, including one for Mr. Rooney. Between that triumph and "The Black Stallion," his career was fully rehabilitated. A further success came with the 1981 television movie "Bill," in which he played a mentally disabled man who ventures out into the world for the first time. He won an Emmy Award for the part.

He was born Ninian Joseph Yule, Jr., on Sept. 23, 1920, in Brooklyn, into a performing family. His parents, Joe Yule and Nell Carter, were vaudevillians, and by the age of 17 months young Mickey was performing. His parents divorced when Mickey was three years old. He made his first film appearance in 1926. Soon after, he played the lead character in what would become the first of many short "Mickey McGuire" films. He became a contract player for MGM in 1934.

In recent years, he found much work lending his voice to animated features and animated television series, and enjoyed yet another comeback as a feisty security guard in the hit film "Night in the Museum." In 1983, Mr. Rooney was given yet another honorary Academy Award.

With movie appearances stretching from 1920s to 2010s, Mr. Rooney's career was one of the longest in cinema history. Throughout it, he maintained a very vocal lust for life and for acting. "I don't regret anything I've ever done," he said. "I only wish I could have done more."