For me, pet names are part of the toon theme.
I have Bridezilla with the following Demons:
Tier 1 - Bridesmaid, Groomsman, Ring Bearer
Tier 2 - Maid of Honor, Best Man
Tier 3 - Groom
Similarly, I have General Mills (Cereal Killers theme with RL friends) that has the following Demons:
Tier 1 - Fruit Brute, Boo Berry, Franken Berry
Tier 2 - Sonny Cuckoo, Trix Rabbit
Tier 3 - Lucky Leprechaun