I'm not typically someone to put animals in sweaters if it's not necessary (My mom's dog with super thin fur taught me that in some cases, it definitely is necessary.). But a friend of mine asked me to make a sweater for her cat since they were doing ugly Christmas sweater pictures this year. I couldn't resist.
Mostly, I modified making a dog sweater and extended the arms a little to accommodate longer limbs on her slender cat. I used my cat as a model for sizing, because she told me he was big but slim. Based on some of the pictures I'd seen of him, they looked close enough in size to make the appropriate estimations.
I did not make it an ugly Christmas sweater. I used a deep red yarn, knitted a long neck in a rib stitch that could fold over like a turtle neck sweater, and used one of my weave knit patterns throughout the whole body.
I can't say the cat was very pleased, but it turned out well, and was perfect for what they needed!