Know Your Meme defines Rule 63 as:

an internet adage which states that for every fictional character, there exists a counterpart of opposite gender.

And this is never done more creatively than in the realm of cosplay. If you have ever been to a comic, sci-fi, anime, or (any type of) genre convention you will have seen gender swapped versions of all types of characters from a female Batman to a male Storm to even Lady Doctor Who.

Which brings me to this snazzy looking lass who is cosplaying as a Rule 63 Doctor Strange (cosplayed by Jennifer Van Damsel and photographed by Isidro Urena Photography):