I never purposefully set out to define my dreamy villagers, but I invite villagers to my island and get a "feel" for them, and some of them have just stuck and I couldn't imagine my island without them.
It has a lot to do with how attached I get to them, their personality, and the interactions I have with them. My absolute never leaves are Agnes and Louie (my ACNH starter villagers), Patty, Rhonda and Savannah.
Savannah was a surprise because I invited her to my island thinking she was cute and she might stay a little while then move on, but she is always sweet, always smiling and sings around the island, rain or shine. She adds something very wholesome and positive to the island.
I love all of the villagers on my island, but I am planning to invite some other villagers to feel if we're a good match.
I've been thinking of inviting Maple lately. We'll see! 

It has a lot to do with how attached I get to them, their personality, and the interactions I have with them. My absolute never leaves are Agnes and Louie (my ACNH starter villagers), Patty, Rhonda and Savannah.
Savannah was a surprise because I invited her to my island thinking she was cute and she might stay a little while then move on, but she is always sweet, always smiling and sings around the island, rain or shine. She adds something very wholesome and positive to the island.
I love all of the villagers on my island, but I am planning to invite some other villagers to feel if we're a good match.