The Narrator character is not only the narrator of the story being told, but can appear as a character in the story. However, it's the creator's decision to make the narrator a part of the cast or not. Whether or not the narrator in your story will be apart of the main cast, here's an article about how to make the narrator an interesting and likeable character.
The Narrator is the Story TellerThis is the guy in charge of telling your story. Whether this character is some kind of Author Avatar or another character completely, this job is important! Make sure your narrator tells the story the way you want it, in a way that brings the reader in the story and makes the reader want to know more. The narrator is usually reliable, but having The Watson for the narrator can help the reader think about the situation in the story really think deeply, even telling the reader what they might've overlooked. An Unreliable Narrator can make readers confused, but can be fun to play around with if you do it right. The Posthumous Narrator can be a character in the story, but depending on who is is, it can either work out or sink... Choose what kind of narration you want carefully. Make sure the narrator brings out the story you have.
How Is The Story Being Told?An important tonal decision to make is whether your narrator is aware s/he is telling the story. The Catcher in the Rye, for instance, is very specifically a novel-length monologue by Holden Caulfield, being told to you while you visit Holden in a mental institution. The titular Jane Eyre takes it a step further by directly Breaking the Fourth Wall to address the audience directly ("Reader, I married him" is how the final chapter starts). However, other first-person narratives are a sort of on-the-spot record of what's going on in the person's head, such as Twilight and A Song of Ice and Fire. These novels present the thoughts of their narrators (Bella Swan for Twilight, Loads and Loads of Characters for Ice and Fire) as they have them, not after the fact. Precisely how the author stole those thoughts out of the characters' heads is typically not addressed. This decision can alter the story, because when telling a tale "after the fact," we have time to work on the presentation. Whilst writing, we often go back to smooth the prose, and to make sure we have actually said what we are trying to say; an oral recitation can also involve this sort of Verbal Backspace. This is why All First Person Narrators Write Like Novelists. There can also be poor recollection; How I Met Your Mother, whose lead character is narrating the story to his children some 20 years later, famously has an episode in which one of Ted's dates goes by "Blah Blah" simply because he can't remember her actual name anymore. It also allows the prospect of an Unreliable Narrator—someone who is either unwilling or unable to tell the whole truth—to rear its mysterious head. Doing this is difficult, since the narrator's lies need to be self-obvious, but can really add to the narrator's Character Development; the lies we tell ourselves are potent indicators of our priorities and weak spots. HIMYM also tackled this, though largely in its contentious finale (in which the story of "How I Met Your Mother" actually turned out to be, "Why I Want To Get Back Together With My First Love"). Compare this with the technique used in "on the spot" narratives. While Holden can conceal certain things by simply skipping them (and, indeed, it's believed that he glosses over being molested as a child), when we hear from Bella Swan or Katniss Everdeen or Tyrion Lannister we assume they are telling us the unvarnished truth. After all, we're hearing their thoughts at the same time they are: there's no time for Verbal Backspace or other self-censoring. This kind of "in-the-moment" narration requires a bit more Willing Suspension of Disbelief, since there's no Framing Device whatsoever, though if it works it has a greater sense of urgency and propulsiveness. (It's the only way to make a first-person death scene work, as anyone familiar with The Red Wedding can tell you.) It gives you room for unflattering characterization, since our thoughts are not always kind—though, if the Hatedom for Twilight is any indication, your characters may find this held against them regardless. Finally, there is enormous room for a deconstruction of the entire trope, with your narrator becoming aware that readers are peeking in to his or her thoughts. However, this is even more likely to toss readers off the Suspension Of Disbelief train, since they now have to accept their own ability to mind-read via book.
The Narrator is The Chick?!Having a member of the main cast narrating the story may be difficult for some. Since most literature is written in third-person from a seemingly omnipresent narrator, or told in first-person from the main character's point of view, having a narrator that's not the main character may seem like a strange idea to some. To do this the following options may work:
The Narrator is Me! I'm the Hero!Having the main character being the narrator is typically done by having the hero tell the story in the first person or Narrating the Present. However The Hero can be the narrator through Let Me Tell You a Story and that hero was me. Depending on the hero being Book Dumb, Book Smart, Genre Savvy, or whatever else can make narration different. It can show how The Hero changes during the story, what lessons they learn, who they come across and how they are maturing throughout the story. This is something to consider.
The Narrator is the Omniscient Being We All Thought he wasHaving the narrator telling the story in third person is typical for most works. But making the narrator an omniscient being who Breaks The Fourth Wall and addresses the reader directly isn't. Having the narrator address the reader through comments at the end of each chapter, through normal narration, or being introduced at the beginning of the story can make the narrator seem alive, like a real person. This can be done creatively in manga or graphic novels, giving the narrator a face and body to call their own, having them appear in their own segments. Typically this is done by giving the narrator no real features, covering up their faces or hiding their identities. However giving the narrator an actual face and body can make the reader feel comfortable and make the narrator more relatable.