"'Who’s on First?' plays, of course, on a series of misunderstandings that is carried by rat-a-tat wordplay. Costello cannot grasp why Abbott’s roster includes Who at first base, What at second, I Don’t Know at third, a pitcher named Tomorrow and a catcher named Today.
Costello is as addled as Abbott is certain.
What makes it funny, Seinfeld says, is that neither man is listening to the other — and that each man is totally convinced of his perspective.
Costello: 'You know the guys’ names on the baseball team?'
Costello: 'Well, go ahead. Who’s on first?'
Costello: 'I mean the guy’s name.'
Costello: 'The guy playing first base.'
Costello: 'The guy on first base.'
Abbott: 'Who is on first.'"