It's Shipoopi from The Music Man. Seth McFarlane is a musical nut, and includes lots of this sort of thing. It tends to be funny if you get the reference, tedious if you do not.
My favorite was the shot by shot re-creation of "Somewhere That's Green" from Little Shop of Horrors. I had seen that movie and thought it was hilarious. My brother (a huge FG fan is ever there was one) had not and just wanted it to end.