A small though slightly tubby little unicorn pony, Buttermilk generally blends in with the crowd pretty well. In public she will usually wear a big sweater to hide the fact that her teats are, well, a lot larger than the average mare.
Yup, puberty hit this little filly pretty hard. She's not embarrassed about it by any means, she just doesn't like drawing attention to herself.
And despite having never been pregnant, her teats require regular milking, or else they'll get swollen and sore. Her milk is quite delicious, and has a very rich and creamy taste.
Don't tell anypony, but she sometimes uses it in her cooking~

She can usually be seen wearing two little red ribbons in her mane, and on special occasions she'll even tie little bells to them.
Sometimes her mane gets so poofy it completely obscures her horn, making her look like an Earth Pony. Good thing it doesn't affect her magic in any way!