AFI #091 Bud Abbott as Dexter Broadhurst, The Naughty Nineties

Sebastian Dinwiddle: I'm not asking you who's on second.
Dexter Broadhurst: Who's on first.
Sebastian Dinwiddle: That's what I'm trying to find out.

- Bud Abbott as Dexter Broadhurst from The Naughty Nineties (1945)

The bolded line is ranked #91 in the American Film Institute's list of the top 100 movie quotations in American cinema.