In KMS, all characters can use three pets, without need for Pet Snack. So, over there it makes sense to give Pink Bean three pets.
The event was copied as-is, and nobody at Nexon realized that three pets and no Pet Snack don't work in GMS.
The sadder thing is that this is the third time we are getting this event. People complained about the three pets the last two times, too. Nothing was changed.
I've forwarded the issue again. Hopefully next time it can be fixed.
Disclaimer: The following is my own opinion and conjecture, and is not based on anything I have been told as VFM.
You know how sometimes we get bugs fixed, and then the fix comes undone at the next major patch? Or text that was already in English goes back to Korean?
This leads me to believe that whatever Nexon uses for code version management (software and/or procedures) is very flawed. And is definitely unsuitable for anything like what you describe. There would be no practical way to merge this "side project", once it's "done" (are such things ever truly completed?) back into the main development tree without the whole game breaking down.