A portion of an Iwata Asks feature on New Super Mario Bros. Wii…
Miyamoto: We started off by doing tests to see how it would feel for the player to control a large character, double the size of Mario. As it felt really good, we continued to develop the idea. But then we discovered that it was more satisfying if Mario only increased in size partway through the game, so we decided to make a small Mario as well.
Iwata: By collecting a mushroom, Mario increases in size to become Super Mario. But why a mushroom?
Miyamoto: Well, the mushroom… When you think about Wonderland, you think about mushrooms, right? (laughs)
Miyamoto: Some time ago I was being interviewed and I spoke about Alice in Wonderland. But it seems there was some misunderstanding and it’s since been stated that I was influenced by Alice in Wonderland. That isn’t the case. It’s just that there has always somehow been a relationship between mushrooms and magical realms. That’s why I decided that Mario would need a mushroom to become Super Mario.