Rule 34: If something exists, there is porn of it

According to Know Your Meme:

Rule 34 is an Internet adage in the "Rules of the Internet" list of protocols and conventions which asserts that "if something exists, there is porn of it." The humorous concept is commonly illustrated through fanarts and fanfictions in which fictional TV and cartoon characters engage in sexual behavior, in similar vein to the Ruined Childhood meme.