Superhero RPF is a fanfic about fanficers so it has a lot of fanfics in it. Most just referenced by their title and summaries, except For Asgardia!, by a guy going by the username Sassgardian, from which there are excerpts all around the fic. It get's him accused with Draco In Leather Pantsing for his heroic interpretation of Loki, and when his identity comes out, he is in fact Loki, with writing Self-Insert Fic.
In Equestria: A History Revealed, the Lemony Narrator writing the fic-essay decides to go out drinking and just copies a large block of test from a book on a soldier's recounting of a significant battle in the history of the Equestrian Civil War into the fic. Notable in that the copied text proves to be vastly different in tone than the rest of the tone of the fic, probably due to its In-Universe copied nature, and is even written in a more high quality fashion than the rest of the essay-fic.
Examples of type 4 (the show is eerily similar to the main show)