Who is the narrator, can she or he read minds, and, more importantly, can we trust her or him?
First-Person (Central Narrator)
The funny thing about Oskar is that he's a first-person narrator who seems to think he's a third-person narrator. Throughout this book, Oskar makes some pretty outrageous claims about what he can remember and what he knows. For example, he claims that he remembers being born: "Let me say at once: I was one of those clairaudient infants whose mental development is complete at birth" (3.32). But claims like this are no doubt Oskar's attempt to sound as though he has been in control of his life from day one. In other words, the guy has insecurities about being vulnerable, which makes sense for a guy his size.
It's because of Oskar's deluded narcissism that we have to be very, very careful about what we believe and what we don't. Obviously, the guy isn't a third-person narrator. But Oskar does everything he can to make us think he's all-knowing and all-seeing, which happens when he suddenly slips into the third person when he says something like "Not one of the sixteen artists noticed Oskar's blue eyes" (37.12). Sometime we even get first- and third-person narration within the same sentence.
And of course, Oskar's the world's most unreliable narrator. First, he may be delusional and hallucinating some of the events he describes. In the second paragraph of the novel, he admits he tells tall tales. He has serious grandiosity issues. And he admits many times that his first version of the story isn't the complete one. He conveniently forgets certain details in the first telling, like the fact that he told the German soldier that his Uncle Jan forced him to go the Polish Post Office. Or that he didn't exactly jump into his father's grave but fell in after his son threw a rock at him.