- narrator breaks free of role as “narrator” to actively manipulate or interfere with the story, converse with characters, etc.

- narrator has a crush on (or major personal grudge against) someone in the story they’re narrating and is verrrry obvious about it

- narrator is the only one able to break the fourth wall; everyone else notices them doing it, but just thinks they’re being weird

- narrator admits in an aside that even though their narration SOUNDS omniscient/authoritative, they are actually just a person and there’s a lot that they’re assuming or flat out making up, throwing the entire story so far into question

- narrator occasionally breaks from telling the story they’re telling in a removed, impartial-ish way to relate tangential personal anecdotes and opinions at great length and with a lot of feeling 

- we finally learn the narrator’s actual, given name in the middle or near the end of the story and it’s strangely, like, touching or cathartic or impactful in some way?

 (i mean, as with most of the list here, this applies to a lot of straightforward first-person narrators, too)