I have an “Animaniacs” cassette in the station wagon, and once in a while, I open the sunroof, pop in the cassette, and start belting out
“Baton Rouge, Louisiana, Indianapolis, Indiana,
And Columbus is the capital of Oh-Hi-Yo!..”
(tune of “Turkey in the Straw”)
Or my other favorite on there
“United States, Canada, Mexico, Panama,
Haiti, Jamaica, Peru…”
(Not sure of the tune of this one - anyone know what it is?)
Wish I could find the book, but someone wrote lyrics to various classical music themes, and I want to find the rest of the lyrics to Dvorak’s Humoresque:
Passengers will please refrain
From flushing toilets when the train
Is standing in the station
I love you…
Another wish: I want to get a copy again of a recording from the 70s: the weather forecast for the British Isles done in the style of Gregorian Plainchant. I heard this on a local classical station, managed to tape a copy on my 8-track player, and BAM!, it disappeared. 
Okay, it’s not exactly a song, but Anna Russell’s 20 minute synopsis of the 20 hours of Wagner’s Ring Cycle from “The Anna Russell Album?” (she sings soprano, alto, tenor and bass parts, mmkay?) still brings tears to my eyes.
And for complete classical comedy songs, nothing beats The Glory of Human Voice (Florence Foster Jenkins) WARNING! If you have any sense of pitch or musicality, chew off your left arm right immediately and escape, especially from the constipated tenor of the duo singing the trio from “Faust”.