Not only one internet rule is included in this pic.

there are two or three versions of rule 63 and the most accepted and known is:

-"It is possible to find genderswapped versions of every fictional character, especially as fan art on the internet." - Wiktionary <Link>
A more descriptive version of this rule is <<Here>>



the rule 35 of internet (related to rule 34) says:"if it doesn't exists, it would or will be made"
the rule Rule 64 says: "If it exists, there's an Alternative Universe of it." (I have 4 and I could be extended those to 5 or 6)


But the rule 63 is not exclusive from internet, this phenomena always there has been existed in any media from before WWII

I could clasify this in 3 situations:

<<counter part of a character in the same universe>>
as part of the plot one sex oposite character asumes a role as the main one following the story, as support or inclusion

Superman <-> SuperGirl
Spiderman<-> SpiderWoman
Batman <-> BatGirl
Hulk<-> She Hulk
He-Man <-> She-ra
The Chipmunks<->the Chipettes

<<Counter part Character in alternative universe>>
what if our hero/villain was born with other gender?

Fin <-> Fiona (adventure time)
Ice King <-> Ice Queen (Adventure Time)
Goku <-> Caulifla (Dragon Ball Super)
King Julien <-> Queen Juliette? (All Hail King Julien)

<<Counterpart characters in other companies as improvements, tributes, parody or spuffs>>
not equal names, no references but definitely they are

Plastic Man (DC Comics)<-> Elasti-Girl (Incredibles Disney)