I made some of these pet beds for our local Humane Society. On some of the beds I made "pockets" and attached a string with a "mouse" toy filled with catnip, which I tucked inside the pockets. Esp. the cats, they spend most of their time in cages where there's really nothing for them to do except sleep, eat and you-know-what. I thought that they could at least have a bit of fun batting the toys.
The only thing I found out was it is important not to use foam as stuffing. They use industrial type washer and dryer that are so hot that the foam melts inside. Oooops on that.

That is a neat and generous thing for you to do.

Is there a particular size that is needed?

Looks like your quilt inspector is making sure everything is suitable!

Standard cage size. I measure the ones I see in the pet stores. The HS have different size cages.

She's smelling the catnip....I told her "It's not for you." So, she just looks.

They are cute! What did you use on the inside?

Aha, right up my alley! in the Jinny Beyer Puzzle Balls book there are lots of patterns for lovely balls. I make a ball to trade for services (hmm) and donate one to the humane society through the local vet. That way kitties waiting to be adopted have something to play with. I use catnip from the health food store to mix in with the batting.

After the Society told me that foam would only melt, I started using polyfill batt. The HS will really appreciate any pet bed you donate. Some people donate knitted or crocheted blankies.

What a wonderful thoughtful thing to do. I bet the pets really appreciate them. I see your own fur baby likes them too.