Throughout the years, the Mags have accrued plenty of critters & creatures, of varying sapience and awareness. The folder is more of a catch-all for things that live in Magtown alongside the Mags and have some semblance of free will (moving around on their own, eating, etc). Since it's the Mags we're talking about, the definition of 'pet' gets stretched.
This box is too big for how little information I put in it. Here's filler text.