Sonic werehog alert.
This is going to turn out like the speculation over the silhouettes of Rotom's forms. People are going to argue over what it is, and in the end they'll all (more than likely) be wrong.
That was me, but it's really sort of a stretch and me just being overly optimistic.I remember someone posting about it being a Smeargle; that makes sense.
It could have used its' art power to imaitate Ash, or it could've Sketched Transform and used it.