When organizing their crew, most people like to sort their petz by breed. In bred petz, breed is conventionally determined by face. It can sometimes be a bit challenging to figure out which breed a pet is, but luckily there's one handy way to check: by simply looking at a pet's "pick a pet" image. Each breed - or rather, each type of head/face - bears slight differences in this image. Since some of the breeds look a lot alike in-game, it can be easier to tell them apart this way. Below, you'll find a brief discussion of how to recognize each breed using the "pick a pet" image. Additionally, for quick reference, you can find a basic image of all the breeds here.
The Alley Cat is super easy to discern by its angry, odd-sized eyes. The B&W Shorthair tilts its head backwards, with somewhat angry eyelids. The Siamese has the same angry expression, but tilts its head slightly forwards. It can also by recognized by its narrow, triangular face, which does not have rounded jowls like the other breeds. The Calico and Tabby both hold their heads horizontally, with relaxed eyelids. Between these two, the calico has smaller eyes (the tabby's eyes are big enough to touch), but the muzzle balls are bigger. The Chinchilla Persian and Persian are the only pink-nosed breeds. Furthermore, the Chinchilla's face appears larger and more detailed in the "pick a pet" picture. The Maine Coon's eyelids are relaxed, and its head tilted forward. One if its eyelids is perfectly horizontal - the same is true for the B&W Shorthair, but this breed has an angry expression rather than a relaxed one. The Orange Shorthair has large eyes sporting a more or less relaxed expression, and a rather big nose. Its chin ball appears a bit misaligned to its muzzle. Finally, there is the Russian Blue, which is more turned towards the camera. It can be told apart from the Alley Cat (which is also turned towards the camera) by its relaxed eyelids.
Petz 5 breeds
Unfortunately, the "pick a pet" image approach does not work so well for the Petz 5 breeds. This is because these breeds are mostly based off of Petz 3/4 bases, and as such, they pose the same way in these images. In fact, figuring out which breed each of these is based on makes good practice. The only obvious exception here is the Pug, which can easily be told apart from the other breeds by its intense squint.