If either nothing or everything has to change, I hope that nothing does, which may mean the songs are simply not parodied, or that they are repurposed.
Here I have copied my Completely different takes on songs
category, and included bad examples, which can be traced to mistakes I and my readers made.
Because the bad parodies do not actually appear on my site, the links on their titles instead lead to the original songs, so you can easily find out how much potential they waste. They are distinguished from the good parodies because their titles are struck out and bold, and have notes underneath them.
You know it is forced if it resorts to a phrasing like that.
I actually wrote this, about Elizabeth. Later, I realized she was the wrong character for the song.
Changing a song completely is not worth it if it makes rhyming impossible.
He Is the Deranged of Deranged
Pirates could have related to this song about freedom. You know why else it is completely different? Because unlike the original, it is not grammatically coherent.
When the enemy torments you with his organ playing, you need not strip complaints about music away from a song. Not entirely, anyway.