Meme

An inside joke derived from a popular "meme format", the origins of which are often procured from a normal (not inside) joke, a celebrity's actions, social media (youtube, 4chan, facebook, etc.), regular media (popular video games, movies, tv shows, songs, etc.), or even other memes.

Memer (One who creates or otherwise spreads memes): "Hey mom, check out this nice meme!"
Memer's Mom: "You're adopted."