A large pack of Diictodon feliceps(the number seems to vary) that will literally gnaw through anything to find out if it's edible. Feel free to play them getting into things or interacting with your character even if I'm not around...they're pretty much always present. You can even make one for your character to take home if you like.
A large colony of cat-sized, shell-less turtle-lizards with tusks. They tend toward earthy colors; browns, greys and whites with streaks and spotting.
This vid pretty much portrays them the way I'm playing them: https://www.youtube.com/watch?v=ABsqOMh2Fyk
Tusks(mostly used for digging and unearthing roots, but also as defensive weaponry) and a seriously mean turtle-like beak. They can easily remove fingers, or large chunks of flesh if forced to bite. Their claws are blunt and negligible as weaponry, though good for digging.
Although strictly herbivorous, they will chew on anything to find out if its edible or not and seem to be a bit likt tiger sharks in that they'll consume completely inedible material and then just hack it back up if it doesn't digest. And they dig and rip apart everything else. There has yet to be a substance presented to them(rock, metal, whatever) that they haven't been able to scrape or gnaw their way through. Also they seem to be...indestructible. Nothing gets rid of them. If you squash one flat it pops right back up, etc., etc.
They have the attention span of hyperactive goldfish on speed. They're very easily distracted from whatever they're currently destroying by some new and more interesting object. They are also non-sapient, and communication is limited to expressions and vocalizations indicating mood. Oh and they love shiny things. They're constantly stealing bits of this and that to decorate their burrows with.
They seem very cat-like in personality, despite their tendency to form a pack. That is, they're generally calm and more or less chill with people and or their surroundings. Feed one and you've made a friend for life. They seem to enjoy attention, affection and head and chin scritches. They will, however, give a nasty bite if startled or threatened.
No one knows. They just...appeared one day, literally right out of the walls. Now they infest the Vagabond and make nuisances of themselves.