Tribbles {wiki} appeared in a 1967 episode of Star Trek: TOS and returned in the spin-off series and movies. Romulan Whore posted this diagram of the inside of a tribble, and attributed it to the Star Fleet Reference Manual. Since there are quite a few such manuals, I don't know who the artist is. http://scarlettohara.tumblr.com/post/529852763/anatomy-of-a-tribble-from-the-starfleet-reference -via Buzzfeed...