The cure for earworms is bollywood, the cheesier the better. For instance: It pushes the earworm out, and leaves without getting stuck itself. (also cheesy bollywood songs are just great anyway)
brain mashup: you load sixteen shells and whaddaya get another day older and a red corvette st peter doncha call me, oh can't you see I kicked that mule to the top of the tree
I just turned fourteeeeen, and I think this year I'm gonna be mean Dooon't mess with meee I'm a big boy now and I'm very scaaaryy~ Doo doo-do doo, dodo doo-do-doo do doo do doo-doo~
Me: *forgets earbuds home one time* My traitorous brain: (Content warning: brownface, enlightened atheism, the whole thing is in extremely bad taste)
This one might not count because it was written down, not an actual tune, but there was a weird webcomic I flicked through a while back which had a musical scene, and the song from it has been stuck in my head on and off for YEARS. "You're-" "No, you're-" "No, you're-" "The someone I adore..."
The creator has apparently apologised for the slur in the words and up-to-date versions exist with a censored spot and name. Personally I think the line should be reworked to be a full line which doesn't use the slur rather than just leaving a gap, but either way, it sticks in your head.