Finish stretching, the critter glances around, sees that there's, well, literally nothing of interest besides some strange new person... And promptly turns around to start batting at Merlin's long hair.

"One of the sorts of creatures that's appeared in this world." The mage is apparently just going to ignore the creature's antics for now. "As you can see, its appearance seems based on a mixture of animals, some from different worlds from each other. This one simply started following me around."

And then Merlin may have started the process of making it into a familiar within a shared dream not long ago. Not that the effects of a dream carried over into the waking world, of course, but some of the impressions and memories of the experience certainly did.