I'm briefly looking into the game again, and I've seen some deers smaller than others in pics with adult coats. Is deer size something that can be adjusted?
Size cannot be adjusted per say. You can only have one smaller size, which is what we call the "mini" size. To get the spell cast on you, you need someone to fall asleep inside one of the mushroom circles. It might take some time before you get it though, as this may turn you into an animal instead.
If you're planning on getting it, keep in mind your pelt will not show whenever you load your set or log in. In order to get it back, you'll have to do this:
1. Approach the Twin Gods' statues.
2. Press escape and go into the menu and the log in screen. Open the action bar at the bottom so you can see all of the actions.
3. Sneeze off your mini spell.
4. Hit the "pray" action and then immediately load your set, then wait for the devout pelt to appear on your deer.
5. Once the devout spell wears off, you will have your pelt back.
As for fawns: yes, they can wear masks. And even antlers and pelts. But they don't stick for long, so they have to reload their set often.
Size cannot be adjusted per
If you're planning on getting it, keep in mind your pelt will not show whenever you load your set or log in. In order to get it back, you'll have to do this:
1. Approach the Twin Gods' statues.
2. Press escape and go into the menu and the log in screen. Open the action bar at the bottom so you can see all of the actions.
3. Sneeze off your mini spell.
4. Hit the "pray" action and then immediately load your set, then wait for the devout pelt to appear on your deer.
5. Once the devout spell wears off, you will have your pelt back.
As for fawns: yes, they can wear masks. And even antlers and pelts. But they don't stick for long, so they have to reload their set often.