How we cite our quotes: (Paragraph)
Quote #1
"That is another of your odd notions," said the Prefect, who had a fashion of calling everything "odd" that was beyond his comprehension, and thus lived amid an absolute legion of "oddities." (4)
This is an awesome (and rare) bit of personality from our narrator. Okay, so we're not convinced that G— is quite as unintelligent as Dupin and the narrator make him out to be, but it's still true that dismissing things as "odd" is no way to solve crimes.
Quote #2
"Ha! ha! ha!—ha! ha! ha!—ho! ho! ho!" roared our visitor, profoundly amused, "Oh, Dupin, you will be the death of me yet!" (15)
If you've read a lot of Poe, this might make you think that G— will die by Dupin's hand by the end of the tale. No such luck. This is just one of the ways Poe tries to trick us into thinking we're about to embark on one of his usual super-dark tales of murder and mayhem.
Quote #3
"The minister decamped, leaving his own letter—one of no importance—upon the table." (28)
The minister severely alters the royal lady's reality at this moment. By switching the letters, he transforms her from free to trapped. Not so for the royal man, who remains in his own blithely oblivious version of reality.
Quote #4
"Then," I said, "you have been making a miscalculation, and the letter is not upon the premises, as you suppose." (68)
Dupin has a pretty black-and-white version of reality: either something is one way, or it must be another way. And we have to say, this works out well for him.
Quote #5
"So, as I knew he would feel some curiosity in regard to the identity of the person who had outwitted him, I thought it a pity not to give him a clue." (122)
Here's a rare moments in this story where a character wants to reveal, rather than alter or conceal reality. This fits in with Dupin as being the only character who can really see real reality. (Is that real enough for you?)