Masks, pelts, and antler only stay on for a short while when you are a fawn, but if you still want them I'm sure someone can cast them on you. You should try playing with other little fawn by eating mushrooms from trees (for a mask), rubbing against a tree and eating a pine cone (antlers), or sitting next to a sleeping deer (pelt). That way you'll be playing with other fawn, and learning about the magic in the forest.

A side note, do not cast spells on mini deer (not fawns, they are just miniature deer) because they cannot "sneeze" the spells off like normal deer can. So, please do not cast on them.