Louis Francis Cristillo (March 6, 1906 – March 3, 1959), better known as Lou Costello, was an American comedian, actor and producer. He was best known for his double act with Bud Abbott and their routine "Who's on First?".
Abbott and Costello, who teamed in burlesque in 1936, were among the most popular and highest-paid entertainers in the world during World War II. During a national tour in 1942, they sold $85 million in war bonds in 35 days. By 1955, their popularity waned from overexposure, and their film and television contracts lapsed. Their partnership ended in 1957, after which Costello made numerous solo appearances on TV and starred in one film.