Turbine's very good at giving NPCs personalities ... and having them remember you. They got their hand in during AC2, when there was (for example) a whole family of Lugians outside Keidelur, each of which had a problem s/he needed help with, but they didn't trust you because they didn't know you. You had to talk to each one of them, and FINALLY one of them would ask you to do something, and when you'd done it, a few of the others would open up.... I spent the whole first day of the patch just doing errands for that family, and thereafter whenever I dropped by, the pet Reedshark would purr at me and the old matriarch would say, "Tapuaua, good to see you again! Can you stay for dinner?"