Tune of “The Old Gray Mare.” Or, if you prefer, “Greasy Grimy Gopher Guts” :
Here comes (insert name here) floatin’ down the Delaware
chewin’ dirty underwear
couldn’t find another pair
five days later, eaten by a polar bear
poor old polar bear
Several very minor variations have been going around since at least the 1950s. This is often coupled with a Row Row Row Your Boat Parody about killing the teacher.