Earliest reference I've seen to "Who dat?" is from WWII. A tension-relieving thing among flyers coming back from a mission. Someone says "Who dat?" on the radio, gets answered "Who dat say dat?" followed by "Who dat say 'Who dat say dat,'" and so on until everyone checked in.

I always supposed it was part of a vaudeville routine or something like that, but I never found out.

Ugga ugga boo, ugga boo boo ugga--

clint

yeah, I remember "Who he?" from Pogo