Ummm... Is Mario really a good guy?

[TomGuycott]

Well in later games the mask actually shows off a crudely drawn fang face rather than the blue Mario face. However, it does nothing magic either, so one could still argue its the brush that transforms him, but it still works to counter that same theory at the same time.

I'm sure Miyamoto knows, and he's sitting in his ivory tower laughing at our theoretical squalor.