Rule 63 is an internet adage which states that for every fictional character, there exists an opposite-gender counterpart. It is considered a notable tenet of the anonymously-written Rules of the Internet, next to Rules 1 & 2 and Rule 34.
For every given male character, there is a female version of that character.
For every given female character, there is a male version of that character.
Rule 63 was first introduced as part of the expanded edition of Anonymous’ Rules of the Internet, most likely published in the summer of 2007, based on Google Insights. The Urban Dictionary entry for “Rule 63” was first submitted by user InternetHateMachine on August 8th, 2007.
Although Rule 63 is still dwarfed in search interest by the most successful of the “Internet Rules”, Rule 34, over time it has shown fairly consistent growth in popularity. The earliest instance of Rule 63 on DeviantArt was submitted by user Xxescaped-vulpinexX on December 12, 2009. As of May 2009, there are over one thousand instances of “gender-bending” artworks tagged with Rule 63. In late 2009, a Danbooru-style imageboard site Rule 63 was launched. As of April 26, 2011, the site has amassed over 19,968 pictures which translates into over 264 pages of images. According to the tags, the three most popular subjects for Rule 63 illustrations are Axis Power’s Hetalia, Team Fortress 2, and Nintedo characters. The existence of Rule 63 could be attributed to similar themes explored by other rules like Rule 28 (“Always question a person’s gender, just in case it’s really a man.”), Rule 34 (“There is porn of it; no exception.”) and Rule 35 (“If no porn is found at the moment, it will be made.”). Such gender-bending art has been also observed in the realms of Alternate Universe and Trap artworks.
It is important to point out that the rule only applies to fictional characters, and not to real people. However, this does not necessarily mean that there cannot be Rule 63 art of real people, which in fact does exist. Also, canonical instances of a genderbended character do not count as Rule 63, whether the alternate gender version of the character is the actual character or the gender counterpart of a character. According to Urban Dictionary, the only exceptions are that “A: the male character is already so androgynous that a female version would be basically the same, or B: the female version hasn’t been drawn yet”.
On June 23, 2011, Salon.com reported that the Futurama season 7 premiere airing that night would feature gender swapped versions of the characters.