I remember for the first six episodes or so of the first season of Red vs Blue, the guys would make up their own opening theme song. I specifically remember one with Burnie singing "I am Red I'm fighting with the Blue, I am Blue I'm fighting with the Red. Why don't we just get together, make ourselves a little Purple."
However, I can't find these videos anywhere. None of the videos on YouTube has the original openings, none of the videos on this site and the DVDs don't have openings to the episodes at all. I tried going to the WaybackMachine, but it couldn't find redvsblue.com or roosterteeth.com.