It's Pokemon but the Gotta Catch 'em All is expanded upon into furniture, bugs, fish, art, villagers, stamps, clothes, rare tools, friends, enemies, TBT, TBT collectibles, fan fiction, and nicknames.
I noticed anything that's relatively a virtual realistic based game gets pretty addicting. I think of Sims, Pokemon, etc. And, it's just so darn cute, idealistic, and happy, who wouldn't love Animal Crossing? ^_^