You can certainly perform a ritual to strengthen the and celebrate/recognize the bond, but it's not necessary.
If you haven't already, try performing an unimportant ritual with kitty in the room. Sometimes an animal is lovely and calm in everyday life but will flip out from ritual elements. They might be freaked out by the energy (either its nature or its intensity), vocal vibrations, or candles and incense. They can also sometimes be fidgety and you don't want to risk your familiar barging through your circle.
I have a familiar-like relationship with my cat, but she's just too skittish to truly act as my familiar.