I also want the answer to this question. I am a little worried to keep my very favorite pet active, because I don't know if there can be a negative result...

if you visit the Ultimate Zapper and somehow make it work (for instance if you think you are zapping yourself but hit the wrong button and choose zap your pet instead) it can be changed species and color.

There are no Random Events that are harmful.

If you take any of the empty containers you can fill at Peka Glade and use them on your pet, it will turn into the camellid Experiment.

Thank you very much, that was helpful information.

no, nothing bad can randomly happen to your active pet. there are random events that can happen to any of your pets, but none of them are negative - one adds a treasure slot to one of your pets, and another gives one of your pets some random stats. you might accidentally zap or use an item on any of your pets, but there's no reason to fear keeping a particular pet active, unlike some sites with random events that can change the color/species of your active pet.

Yes exactly, and I have a special red-panda-moth that is one of the rare experiments, I would never want to change him into anything else!