On all three Christmas episodes, somebody sings "Deck The Halls" with made up lyrics

Florida, Thelma and JJ sing it on Sometimes There's No Bottom in the Bottle
example: "Kid Dynomite is cute and jolly, fa la la la la, la la la la"

JJ sings it on Penny's Christmas
example: "The ebony prince is here by golly, fa la la la la, la la la la"

and Thelma, Michael and Florida (Penny too maybe?) sing it on Traveling Christmas
example: "Keith looks better than Muhammad Ali, fa la la la la, la la la la"

I never realized that.