I plan to keep Carmen forever and ever and ever and if she ever moves out I will just scan her back in with the amiibo card I got of her.
Then, when I get Punchy and Felicity amiibo cards, they're never leaving either.
Other villagers I would never, ever let leave: Lolly, Tiffany (because I want to change her catchphrase to wha-psh!), Marshal, Stitches, and O'Hare.
Bud, He's one of my best friends and Starter villager. Also, Curt, a best bud and long time villager back from WW. Stinky and Frita are here to stay. Other than that everyone else is moving. I want to get Gannon pig and Chadder as forever villagers too. Then I'll have 3 rotating spots to always have new villagers.
Fauna. I'm so in love with her. I've just started playing Desert Island Escape and she always does this cute wee tip toe when she's approaching a creature in the bushes. Everything about her is adorable. Also Poncho. I am never letting him move!