"Who's on First?" is a comedy routine made famous by American comedy duo Abbott and Costello. The premise of the sketch is that Abbott is identifying the players on a baseball team for Costello, but their names and nicknames can be interpreted as non-responsive answers to Costello's questions. For example, the first baseman is named "Who"; thus, the utterance "Who's on first" is ambiguous between the question ("Which person is the first baseman?") and the answer ("The name of the first baseman is 'Who'").
