Accidents happen. Sometimes important accidents happen, like Christopher Colombus discovering America, or the inventor of the popsicle leaving soda out overnight with a stick in it. Videogames are no exception, and sometimes the biggest contributions to games have been entirely unintentional.
Though many of you could not even imagine what life would be like without being able to experience a 1:1 backswing in Wii Sports Resort, golf wasn't supposed to be part of the sequel in the first place. During 2008's E3, Nintendo Superproducer Shigeru Miyamoto talked up how much better Wii golf was going to be in the new game, due to the WiiMotionPlus adapter. The development team had no choice but to put golf in, since he mentioned it in an interview. This was a maneuver that Miyamoto actually referred to as "blocking off the escape route," because that's what happens when you're the Steve Jobs of Japan.
We all live in fear of the frightening sound of Sonic's drowning theme, but it might have never happened. According to an interview with Sonic creator Yuki Naka, the reason that Sonic can't swim in water levels is because he at the time thought hedgehogs couldn't swim. It makes Labyrinth Zone even more disappointing, not just because it was really really hard, but also because it sullies what was once a realistic portrayal of the way hedgehogs curl up in a ball, run really fast, and defeat evil scientists.
Usually glitches in games don't amount to more than an easy way to get lives or making Donkey Kong ride on top of a gray Donkey Kong, but never do glitches amount to something as monumental as The Minus World, an endless water level in the original Super Mario Bros. Though many believe that the minus world (which the game refers to as "World -1," hence the name) was intentional, it was simply a flaw, discovered by someone with far too much time on their hands. To enter the minus world, you have to stand on a pipe at the end of world 1-2, jump backward, go through a wall, and then go into a pipe. It's so convoluted and random, I'm surprised that the game recognizes it as a glitch, let alone humans.
In 2005, Blizzard introduced a new dungeon to WoW with a new dungeon boss. The boss, Hakkar, had a hex called "Corrupted Blood," which, when performed, would drain hit points for a few seconds. Pretty standard stuff, except that it was contagious. People soon realized that they could teleport out of this dungeon, infecting other people in other areas of the game. Soon the game became about one thing: avoiding the corrupted blood spell. It got to a point where terrorism officials and epidemiologists began to take notice of the way that the game was being affected, treating it as a case study. If there's one lesson to be learned from this, it's that you don't have to be a user of World of Warcraft to treat it as serious business on your internets.
There are people who think they are really good at Super Smash Brothers Melee, and then there are competitive Smash players, who take it to a whole other level, abusing the physics of the game and concocting new moves solely in the name of playing as fast as possible. No move is more ubiquitous than "wavedashing," the cornerstone of advanced Smash play. The move involves air dodging into the ground so that you slide really fast. The game, however, considers you to be standing, so you can perform any standing attack. It's much more effective than performing a move while dashing, and is absolutely essential to keep up with competitive players. Unfortunately for those players, Nintendo changed the physics of the air dodge in Super Smash Brothers Brawl, so wavedashing was no longer an option. This, as you can imagine, led to many people ragequitting from the competitive Brawl scene.