For each snowman, thread a branch through three large marshmallows so they're touching. To make arms, place a pretzel stick on the right and left sides of the middle marshmallow. Attach a small marshmallow to the ends of the pretzels to make hands. Lightly toast marshmallows until golden. Arrange mini M&Ms on the top of the marshmallow to make eyes, a nose, and a mouth. Remove branches before serving.