"Fluffybuns" could just refer to Asgore being a fluffy cinnamon roll. On the subject of nicknames, what about Sans' pet name?
Hey it could be! Maybe Asgore’s nickname is more innocent and we’re just the naughty ones.
As for Sans, we haven’t shown it yet (though it was and still is going to appear in the next comic) but Papyrus sometimes calls him “Bb” and River is to blame for that. When he was little, River would refer to him as “Baby Blue” due to his magic color
and being their lil baby and it just sorta stuck. I mean…
Can you see why they called him that? Their Baby Blue~
Dings started calling him that and, while Pap has never said “Baby Blue,” he called him Bb for short. Eventually Tori, and a few others, will learn of this name and will abuse it. He’ll get an array of pet names from Toriel as they grow closer as well.
And we can’t forget the pile of strange and mostly inappropriate names Chara has for him. Bone Daddy being one of them. I could go down a list but then we would be here forever.
This child needs parental help.