DEAN: You’re going to build a house?
RORY: It’s for charity and I’m late, and why don’t you go on inside and you and my mother can continue the “Rory’s building a house” routine, and when that gets boring you can move on over to “Who’s on First?”
“Who’s on First?” is a famous comedy routine by Abbott and Costello, in which Abbott is identifying players on a baseball team for Costello. The comedy comes from the fact that their names sound as if they are answers to Costello’s questions. For example, the first player is named Who, thus the answer to “Who’s on first?” is “Who’s on first”, leading to utter confusion.
This was a style of routine very popular in the early twentieth century, and Abbott and Costello had a big hit with “Who’s on First?” in a vaudeville revue in 1937. In was performed on radio in 1938, and copyrighted in 1944. Abbott and Costello performed it numerous times in their careers, rarely the exact same way twice, and performed it for President Franklin D. Roosevelt several times.
Abbott and Costello included a shorter version of their routine for their 1940 film debut One Night in the Tropics, and a longer version for their 1945 film The Naughty Nineties, considered their best recorded version of the routine. The “Who’s on First?” bit they did for their 1950s television program The Abbott and Costello Show is considered the definitive version.