One of the first PC games I played! As far as I'm aware there is still has an active modding community that makes custom items and pet breeds.
The games that followed this removed the ability to breed the Petz and that for me was the most fun part. Seeing what would happen if I mixed weird combinations etc. Being able to make your own custom areas to take your pets was great too.
Unfortunately, the original release of the game had an odd bug where after a while of having both Catz 5 and Dogz 5 installed to make "Petz 5", the game just refuses to open after being in use for X long. It would be great to see this bought back and with a fix for that problem!