<P> Bud Abbott stated that it was taken from an older routine called "Who's The Boss?", a performance of which can be heard in an episode of the radio comedy program It Pays to Be Ignorant from the 1940s . After they formally teamed up in burlesque in 1936, he and Costello continued to hone the sketch . It was a big hit in 1937, when they performed the routine in a touring vaudeville revue called "Hollywood Bandwagon". </P> <P> In February 1938, Abbott and Costello joined the cast of The Kate Smith Hour radio program, and the sketch was first performed for a national radio audience that March . The routine may have been further polished before this broadcast by burlesque producer John Grant, who became the team's writer, and Will Glickman, a staff writer on the radio show . Glickman may have added the nicknames of then - contemporary baseball players like Dizzy and Daffy Dean to set up the routine's premise . This version, with extensive wordplay based on the fact that most of the fictional baseball team's players had "strange nicknames" that seemed to be questions, became known as "Who's on First?" Some versions continue with references to Enos Slaughter, which Costello misunderstands as "He knows" Slaughter . By 1944, Abbott and Costello had the routine copyrighted . </P> <P> Abbott and Costello performed "Who's on First?" numerous times in their careers, rarely performing it exactly the same way twice . They did the routine for President Franklin Roosevelt several times . An abridged version was featured in the team's 1940 film debut, One Night in the Tropics . The duo reprised the bit in their 1945 film The Naughty Nineties, and it is that longer version which is considered their finest recorded rendition . They also performed "Who's on First?" numerous times on radio and television (notably in The Abbott and Costello Show episode "The Actor's Home", widely considered the definitive version). </P> <P> In 1956, a gold record of "Who's on First?" was placed in the National Baseball Hall of Fame and Museum in Cooperstown, New York . A video (taken from The Naughty Nineties) now plays continuously on screens at the Hall . </P>

Who is on first what is on second