Your pet is a member of your family. I even call mine Baby sometimes (most of the time). They deserve a little something special on Christmas too. This is a list specifically for Cats, however it could be translated into most pets.
First and foremost you need a stocking to place all the items in. There are many options to choose from. You can take a classic red and white stocking, put their name and some cat ears on it. Or go to websites like Etsy and get a custom made one. What ever you choose make sure that there is enough room for all the lovely gifts you want to stuff in it.
Small toys are great stocking stuffers for cats. Not things like the Super Roller Circuit Toy. But small ones that can fit in the stocking. Some great options are: balls, mice, small rod toys, and plush animals. (My cat loves to destroy fox toys, which I think is good because I live in an area where foxes come right up to my door step). My favourite option is a treat dispensing ball.
Which leads me to my next option, treats. Treats can include bags of their favourite treats, or canned food, or cat milk. It could even include cat nip if that is something your cat is in to (mine is not, it only effects about half of cats).
Apparel could mean something like a sweater, mine looks adorable in his Christmas sweaters. But it could also mean a new collar, mine looks adorable in his bow tie. I would suggest putting a new collar in the stocking for him. Especially in the winter when its dark out, a reflective collar is great.
This goes for both human and animal stockings. having something practical in stockings is great. For cats I would suggest a brush or some nail clippers.
I hope this helped you figure with gift ideas for your fur-babies. Is there anything else that you would put in a stocking?