(Illustration comes from artist Daniel López’s DeviantArt page and is © Paizo Publishing.)
As far as I can tell, the chuspiki is an original Pathfinder creation, a mouse with a fan-like tail that it uses to ride the breezes—many of which it creates itself, as it’s also a natural (or rather, supernatural) aerokineticist.
I’m not quite sure the physics of that (I love it in theory, but flying squirrel-like skin flaps seem way more practical, even for a magical beast)…but setting aside that qualm I am all about this little guy. We’ve talked before about using an unusual low-level monster to add early flavor to a campaign, and the chuspiki is that in spades. If your campaign were a manga, you know you’d see these guys on the very first page. Like the sky bisons in Avatar: The Last Airbender or the fire-lizards of Pern or the Slimes of the Dragon Quest franchise, chuspikis instantly set your campaign apart—all the more so because they are magical creatures of air (whether you emphasis the psychic aspect of that magic or not).
And if you’ve already got a campaign underway…well, you need to introduce that hidden valley full of kineticists somehow, right? Or you’re bored of medieval settings and want to turn the whole thing steampunk? A crashed airship with chuspikis as the only survivors should do the trick. Or maybe you just want to reward your party’s chaotic spellcaster with an equally chaotic Improved Familiar? Aero-adventures (Occult and otherwise) are waiting...so give in to the magical mouse with the weird tail.
In order to begin training as an aerokineticist, a young novice must first observe the habits of the chuspikis. His fellow friends (themselves also novice adventurers of all stripes) may accompany him, but all must be careful not to offend the very social, highly intelligent magical pranksters.
Adventurers have adopted—or more accurately, they have been adopted by—a faerie dragon. Which is all well and good, but this faerie dragon has pranked some folks with long memories, including a flock of chuspikis. Time has only curdled the flying rodents’ attitudes toward the dragonet, and they are more than willing to sic gremlins and goblins on the party if their own air blasts and barbed tails can’t do the trick.
Adventures come across a strange metal…ship? Horizontal tower? Flying machine? It’s hard to tell. What’s certain is that it’s infested with strange glider-like chinchillas—that can talk! Most speak a language unfamiliar to the adventurers, but the flock matriarch and her daughters have enough command of Common to explain that the wreck is a former “Sky Tiger,” a kind of airship. With the chuspikis’ help, the adventurers can unearth the Sky Tiger’s lifeskiff…whose psychic magic-infused sails will take the adventurers toward a war they didn't even know was brewing, using technology and occult arts their continent has never seen before now.
—Pathfinder Bestiary 5 56