For Navi, the left cat, we call her Chunka Munk, Plasticat, and Ms. Infected Lips.
For Scorpi, the cat on the right, we call him Mr. Small, Spider Cat, and Crybaby.
ok its not a specific nickname for any cat, but i love calling our boy cats "hantum" [handsome] . i just go "hey hantummm!! hi hantum boyy!" when i see them and they love it