Cat: Mitzi + Purrl (unfortunately I've had no luck finding them in NH)
Dog: I don't have a favourite, but I really like Maddie! I have her on my island right now and plan to keep her
Cat - Kiki! I've never had her before and would love to have her in my town. She has such a sweet and kind of funny looking face!
Dog - Mac and Lucky! (It's a hard choice for sure, though I would prefer Lucky to move in!)
I guess Bow and Meow don't count since they're not in the game, but they're great too and it's a real shame that they didn't bring them back! Maybe someday! c: