Dust Bunny

Little is known about dust bunnies as they are masters of blending in and would rather dissolve into a cloud of dust than be caught and held in captivity. What has been discovered has been through very careful observation through magical means such as the researchers making themselves invisible or watching from a distance with an arcane eye.
Dust bunny is also used to describe a collection of dust, of course, and the species was named for its indistinguishable appearance to exactly that. When seeing a dust bunny move it's natural to assume that it was caused by a breeze which is why the living creatures have managed to stay undetected for so long - that and the aforementioned ability to turn into dust upon capture.
No one knows if they are born and live indoors or if they simply sneak in from time to time. Dust bunnies do seem to like to play tricks on people. If a person drops something that lands underneath furniture, a dust bunny can lightning quick absorb said object - no matter if it's bigger than the dust bunny which does not grow in size in this process. When the person reaches under the furniture for the object it will be gone. Sometimes the dust bunny will spit out an entirely different object for the person to find or, even more remarkably, small living creatures such as bugs or mice. 
Although they do keep some of the things they absorb that doesn't seem to be the point as they apparently give a lot of them back after a varied amount of time; it can be minutes later or even several years. This shows that dust bunnies probably do it because they think it's funny.
Researchers think that the dust bunny's ability to absorb much larger objects without growing in size may mean that it’s got some kind of demiplane naturally within its body, or it's capable of magically disappearing things.