'Shiny' Pets

Besides World of Potter, I love to play Pokemon Go. In Pokemon Go people actually try to get the special shiny pokemon. These Pokemon are special colored and the chances of getting these special colored ones are low. 

While I was staring at my great pet fish, I was kinda thinking about adding that to World of Potter. So when you buy a pet (such as a fish) there is a small chance that you will get a special colored fish. The color of the pet can be decided bij the illustrating team, but think about a gold/blue/pink goldfish, a dotted/spotted pigmypuff or just a lilac colored one. There are multiple options per pet.