I seem to remember the line "..who dat?" from a movie as a kid.

the response was " who dat say WHO DAT?"

then "who dat say WHO DAT when I say who dat?"

Abbot and Costello come to mind.

Who's on first?

by the way, for English purists, it is only proper to ask:

" Who that ??? ".. or whom, izzit?

heckwiddit.