Familiar tunes and old friends.
You're basically a kid, with a face matching your personality, holding the responsibility of living alone away from your parents, into a home of a town filled with animals. That's cool though, because the animals are super-friendly, and will give you furniture, and ask you to do things, and for a while, you'll find yourself talking to your whole town.
They're always saying something different, and you never know what to expect, which is the whole reason this game is sweet: it's just like real life. You never know what to expect. Except for the constant things, like morning sunlight, the familiar tune ever hour of the day, morning cicadas, yellow, green, blue butterflies. The rare beetles at night. The store opens at 8 AM, closes at 11. Buy coffee, and talk to Brewster ever day to get develop a friendship and get different coffee flavors.
Find out which neighbors are your favorite. Send them letters. Get a reply the next day. Send them furniture, they put it in their house. Some move, other move in.
The whole entire game is just innovative. You become part of it, and check out what's up in town every day. It changes as you change. It's like another life.
That's just why this game is a sandbox filled with familiar tunes and old friends...