What I like to call Nibbs when he lays with all his limbs under his body:

Mr. Trunk
Kitty Loaf
The unmovable pet
Rollable pet – fun for kids!
Log o’ fur
Thanksgiving kitty
Turtle boy
Kitty got too hungry one day and ate all his own limbs

K, not the last one, but I think it’s funny. Personally, I like Mr. Trunk. Trunks are funny and it’s a funny word. Hm, am I avoiding studying by doing anything but?