Not really a big glitch or anything, but I thought it was a little interesting.
In Sun and Moon, when evolving a Pokemon, the model of the evolved Pokemon appears near the top-left corner of the screen for a split second before disappearing. At the very least, this has happened to me when evolving Pichu into Pikachu. If I had to guess, I'd say that the model loads in while the Pokemon is evolving, but appears for a very small period of time before it moves off-screen?
I'll see if I can get a picture of it soon. Has this happened to any of you guys?
EDIT: Ok, here's a kind of crappy picture. I took a video too, but there's a glare of my face in it despite all of my attempts not to catch that, ack