Chicago native William O'Leary worked extensively in theater, joining the ranks of Gary Sinise, John Malkovich, William Petersen, and Laurie Metcalf, among many others, who helped make the city a hotbed of vibrant actor talent. After landing a small role in an episode of fellow Chicagoan Michael Mann's cops and mobsters television show "Crime Story", O'Leary worked on Alex Cox's experimental, controversial political satire "Walker". The film is notable for its idiosyncratic, postmodern view of America's illegal military involvement in Nicaragua in the 1850s but also because filming there almost killed O'Leary. He was stricken with severe food poisoning and hospitalized for over two weeks. Another great part for him was in Ron Shelton's baseball romantic comedy "Bull Durham" as a born again ballplayer. His most familiar role, however, was on the long-running ABC sitcom "Home Improvement" playing Tim Allen's brother Marty. Young viewers, especially ones with a taste for Asian action heroes, may know him best as the seething, villainous General Xaviax on "Kamen Rider: Dragon Knight" (an Americanized version of the cult Japanese series). O'Leary appeared in the action film "Flight of Black Angel", the horror sequel "Candyman: Farewell to the Flesh", and the cop show "Karen Sisco". In 2009, he landed a guest role on the real-time action series "24". When not performing in film or television, O'Leary teaches acting as part of his The Actor's Path studio.