9. Super Mario Bros.: The Lost Levels - Poison Mushrooms
In 1986, Nintendo released Super Mario Bros. 2 in Japan. Using a modified version of the original game's engine, it was not what we've come to expect from Mario sequels. Instead, it was pretty damn similar to the original, except for one important difference: It was dramatically more difficult.
As much as games could be insanely hard due to technical limitations back then, Mario creator Shigeru Miyamoto designed the first game very carefully. He wanted video game newbies to have an idea of what to do as soon as they picked up the controller.
Goombas looked similar enough to mushroom power-ups that he wanted to make sure Goombas were clearly aggressors that Mario needed to avoid. So does this have to do with the sequel?
Well, not only did it introduce poison mushrooms, which looked much more like the power up than Goombas ever did and had the same effect as a hit, but one was in the very first item box of the game!
Other than announcing the difficulty spike, t didn't exactly mesh with Miyamoto's stated goals in the original. Nintendo of America hated the game, and it wasn't released outside of Japan until 1993, when it was renamed "The Lost Levels" for the Super Mario All-Stars compilation.