No one's seriously has mentioned Celeste yet? You know, Blathers's little sister, the owl who wears a pink bow in the second floor of the musuem? Yeah, her.
I found her to be really interesting back in WW, letting me make constellations in the night sky. And when she'd get flustered after the player calls her cute, it was so funny seeing her reaction. And I think she also talked about her brother's fear of bugs from time to time and how he tries to cope with it or cure it, if I remember right. lol
But now in NL, she's just a souvenir salesperson, which isn't as cool. But she's still my favorite NPC regardless. c: