You have to respect the geniuses who come up with optical illusions. There's some heavy brain work behind them, and probably some serious computer programming as well, not to mention no small amount of artistry.
Sometimes, though, optical illusions just kind of...happen. Sometimes it's a dress that nobody can agree on the color of, and sometimes it's beach scene that could be a rusted out car. But there's nothing like some classic cloud-gazing to really get into some optical illusions.