How do you come up with catchphrases for your villagers? I try to sort of relate them to the villager's name. Here's an example I made earlier: Cole = Cola = Coca Cola = Coca = Coke = Cokey! (his catchphrase)
Deirdre's catchphrase is "dryad" because her house(and my interpretation of her character) is forest-themed
Diana's catchphrase is "lovely" because it sounds sweet and I feel like it's something she would say a lot("How lovely!" "That's just lovely!" "You look lovely today!" "Hello, lovely!")
Fuchsia's catchphrase is "groupie" because I picture her as being really into the band scene and her character reminds me of a lead singer
So really, I just pick something catchy that matches their character/design. I also kind of interpret their catchphrases more as nicknames they call everyone, kinda like how people sometimes call others pet names like hon/dear/etc.
I usually go for what I think fits them as well. However, sometimes I do themed catchphrases. Since it's around Toy Day, I made Christmas back stories for every villager and have them catchphrases to match them. For example, Muffy is like Scrooge. She doesn't get in the Christmas spirit. Her catchphrase is ba humbug. Marshal resembles the marshmallows in hot cocoa. His catchphrase is hot cocoa. Kyle is a pop singer that does covers for every Christmas song. He refers to everyone as a caroller. Kid Cat is jealous of Jingle and wants to be the REAL well-known hero. His catchphrase is I'm better. Fang is an arctic wolf that misses the harsh weather conditions. His catchphrase is blizzard, as if he's telling the weather to make it blizzard for him. Whitney resembles the snow that falls during the holidays. Her catchphrase is snowflake, and it's also referring to her snooty personality, calling others a "special snowflake". Cherry resembles the cherries you put on top of Christmas desserts at Christmas dinners. Her catchphrase is on top.
I try to make it go with their design, personality, or their previous catchphrase: Kyle's old catchphrase was 'alpha' and I changed it to 'delta' and then 'beta', 'sigma', 'gamma', etc.
For the cutsie characters, I mostly give them pleasant sounding words like, 'sweetie', 'softie', 'dear'
Sometimes I relate it to the current event: 'ho,ho,ho' for Christmas
I usually always just make their catchphrase their original one (of course they think it's a new one, though) or for villagers such as Felicity, I just go with "meow" or "woof" for Cookie.
Since my town name is a JoJo reference, my villagers just say "Za warudo" and "Yare yare daze." I'm sure I could come up with something more interesting, but honestly I'm just too lazy.