"That was the original intention of the game. It was a game charged with the signs of gay culture, and Luigi and Mario were a gay couple trying to face a society that rejects them. Further, when we introduced the game for a western audience, we changed some concepts, but if you observe carefully, many of the original concepts are present. The goombas and the flags at the end of each level are symbolic male reproduction organs.
The princess isn't real, it is an allegory to the traditional female ways, which is similar to homosexuality, and in the game, the lovers go on a constant quest for castles, to finally learn that gay identity goes beyond looking as a woman. The plumbing is another nod to gay culture, and Koopa represents the over masculinity, the macho man and the intolerance, and that's why Mario and Luigi must defeat him" (Shigeru Miyamoto).
Yeah... I'm not making this up, I just read it

I know...