The Tosh.0 Principle describes an increasingly common and rather infuriating occurrence in which an obscure joke, character, story, or other piece of media is referenced in mainstream media, causing everybody to think it originated from the latter.
Named after the TV show Tosh.0, which provides commentary on internet viral videos. Other notorious culprits include South Park, Family Guy, and rap music.
You: "Have you seen that video of the crazy Ugandan preacher talking about gay people?"
Your Friend: "You mean the one from Tosh.0?"
You: "The Tosh.0 Principle strikes again!"
Your Friend: "Hey, turn it up. This is that MC Hammer song."
You: "This is Super Freak, you idiot."
Your Friend: "What are you reading?"
You: "The Call of Cthulhu."
Your Friend: "Isn't that a Metallica song?"