I actually did something similar. In Fallout: New Vegas i would frequently catch myself singing the Ink Spots song "I Don't Want to Set the World on Fire." Usually this happened when i was doing something crazy or violent, my favorite part being when i caught myself singing it when i was beating a group of bandits with a lead pipe trying to see how many giblets i could get out of thee people.
Oddly enough i did the same thing in Skyrim while doing one of my more curious habits of checking the bodies of people i killed with arrows to see if they actually did receive a lethal wound, quietly singing "One More Soul to the Call" as i was trying to determine if my arrow would have pierced the heart of a random Nord bandit.
i started the anti brony movement because you fuckers keep trying to rape us but killing off a whole group of semi-intelligent beings for the actions of a few is genocide well then... i guess a seig heil is in order