Rule 34: If it exists, there is porn of it. No exceptions.
Rule 35: If there is no porn of it, porn will be made of it.
Rule 36: No matter how fucked up it is, there is always worse than what you just saw.
Rule 63: For every given male character, there is a female version of that character (and vice-versa). And there is always porn of that character.

Source: tvtropes.org/pmwiki/pmwiki.php/Main/RulesOfTheInternet