At last I'm not a thread-killer! Somebody reacted...

Here's another possible slant on the topic: parodies whose originals have been largely forgotten. "Gentle Annie" comes to mind (Australian parody of a Stephen Foster song, I believe), also "A Capital Ship" ("the 'Walloping Window Blind'") (I found the original on a CD by Rik Barron). I'm sure I'll think of others, but maybe I'll get back to work and see what other folks come up with.