Scene from "Swing Wedding"; Cover of the libretto for "Who Dat Say Chicken in Dis Crowd." from 1898, found in the Paul Laurence Dunbar Digital Collection of Wright State University.
I linked to the Wikipedia "Who Dat?" entry in a previous post but didn't read it. The ubiquitous chant for America and Freedom's Alltime Underdog Heroes the New Orleans Saints has a more interesting history than I previously knew.
The first reference to "Who Dat?" can be found in the 19th Century. A featured song in E.E. Rice's "Summer Nights" is the song "Who Dat Say Chicken In dis Crowd", with lyrics by poet Paul Laurence Dunbar. A common tag line in the days of Negro minstrel shows was: "Who dat?" answered by "Who dat say who dat?" Many different blackfaced gags played off that opening. Vaudeville performer Mantan Moreland was known for the routine.The article points to the 1937 minstrel-heavy Happy Harmonies/Harman-Ising cartoon "Swing Wedding" viewable on the Japanese video site YouKu. Click here to view it; I couldn't decipher how to embed it. "Who Dat" appears at the 6:00 mark.
Edited to add: the clever and talented DJ Misc figured it out.