Delayed Narrator Introduction

Basically this is when someone narrating the story is introduced as a character part way in and reveals this is who they are (although they might not do so immediatly, this is usually the case). The narrator usually doesn't introduce themselves before this point, so it's usually The Reveal. At this point the narration might stay in the third person, however if the narrator sticks around and follows the protagonist it (obviously) shifts to the second person. A good sign that you're dealing with this trope is a statement along the lines of "...and that's when they met me, [insert name here]".

Naturally this can invoke a bit of Fridge Logic; how accurate was the narrator's previous narration when he wasn't present? While he could certainly have been told about it later he could just as easily be an Unreliable Narrator (although this twist is rarely seen along with this trope unless it applies to the whole story).

This trope often goes hand in hand with How We Got Here (since the narrator's narrating events that took place before he began talking), it may also use In Medias Res if it starts with the point where the narrator joins the story. Often overlaps with Narrator All Along, where the narrator's identity isn't revealed until the very end of the story, as a twist.

Anime and Manga

 * Manzou from Samurai Champloo does this where he introduces who he is after he'd already been the voice narrating.

Film

 * The Arnold Schwarzenegger Conan the Barbarian film is narrated by Mako's character, who Conan meets for the first time partway through. (According to one account, the original plan was for Conan to narrate, but Schwarzenegger's English wasn't up to it.)
 * Peter Parker does something like this at the beginning of the first Raimi Spider-Man movie.
 * The narrator in Carne Tremula (also known as Live Flesh internationally) points out his own birth near the beginning of the film.
 * In the film Gor the narrator doesn't appear as a character until the end of the film; he's the sequel's Big Bad.
 * Sir Anthony Hopkins's character in the film Alexander (about Alexander the Great). Ptolemy was one of Alexander's generals. The Framing Device of the movie is Grandpa Ptolemy telling the childern about Alexander because it is the doom of men that they forget. Young Ptolemy did no narration during the action scenes. Grandpa Ptolemy's function was to tell about big battles which would be too expensive to show.
 * Patou from Rock-a-Doodle narrates the entire movie, but first shows up in person when the Grand Duke is about to eat Edmond.

Literature

 * In the book From the Mixed-Up Files of Mrs. Basil E. Frankweiler, where the Framing Device is that this is a letter from the titular Mrs. Frankweiler to her lawyer to explain why she is changing her will. Mrs. Frankweiler herself doesn't actually show up until almost the end of the story.
 * The identity of the narrator of The Brief Wondrous Life of Oscar Wao isn't explicitly revealed until at least halfway through the book and there aren't many clues (It's, by the way).

Live Action Television

 * In the miniseries I, Claudius, it's around three episodes before the narrator is even born, although it's explicitly a story told by that character from the beginning.

Video Games

 * In Bastion the narrator is a mysterious old man named Rucks. When the Player Character reaches the eponymous Bastion after the first level, he's revealed to be the only other person who made it there and introduces himself in the narration (although he doesn't reveal his name until a bit further in ).
 * The narrator of Valkyria Chronicles isn't introduced until, despite narrating the events previously. How she could narrate events she was not present for is handily explained, since she is an  . This also overlaps with Narrator All Along, since her identity as the narrator is not revealed until the end of the game.
 * In Dragon Age II, Hawke first meets Varric, the narrator of their story, one year after arriving at Kirkwall.
 * isn't introduced in God of War series until after narrating the entirety of the first game and the prologue of the second.