Utu has lots of nicknames, he understands that I only want something from him if I use his real name, the others are just for greetings, cuddling and general talk. Few examples: Uzi, Uzi Mau, Sensei Utu, Uhu (the owl), cheap woman, roadkill..
Kuura: Hello Kuura, seal cub (kuutti in finnish), polar bear (jääkarhu in finnish), arctic/snow fox (naali in finnish), lump (möykky in finnish), meatloaf (mureke in finnish)..
Tomu: Tomu Mau, Tomultrus, Tomudeus I, Tomurder, Ed (the hyena from lion king), Zed (a guy from police academy movies), Silly boy
Luna: Well, Luna is her nickname, Lunazi, Nazi (

), Cotton Candy (hattara in finnish), Fluffy, 'You are so tiny', and sometimes she gets to hear her real name Dascha.
I need to use certain voice to make them realize that I'm talking to them instead of about them, or if I want them to come to me etc. Otherwise they'll just look at the person mentioning their name but will not do anything if the name is not said in a specific tone.

(Most of their nicknames are finnish but I wrote them in english here so you'll know what they mean).