A few years ago I worked with a developer who called himself “Norwegian Bastard” and he refused to accept any errors he made and referred to them as bugs, they were “unwanted” or “undesired features”. After a few weeks of this I had to agree with his self-imposed nick name. But when I came across this article on Quora on bugs that became features I couldn’t help but think of him.
My favourite one being “In the original Space Invaders the level got faster as you killed more aliens. This was actually not by design but a by product of the graphics rendering being processor limited. As fewer elements were shown on screen the rendering got faster.”