Maud Pie (voiced by Ingrid Nilson) is one of Pinkie Pie's Sisters in My Little Pony: Friendship is Magic.
At the beginning of the episode Maud Pie, Pinkie Pie speaks at length about her close relationship with Maud and their tradition of trading rock candy necklaces. She describes Maud as sharing interests with her friends, such as Rarity's love of fashion, Applejack's honesty, and Twilight's fondness for books. When Maud arrives in Ponyville and meets Pinkie's friends, the ponies are surprised by her eccentricities, overall lack of enthusiasm bordering on apathy, and strange taste in games. Maud is shown to have a deep knowledge and fascination with rocks. She also has a pet rock named Boulder.
Each of Pinkie's friends attempt to befriend Maud, but her odd tastes and interests at times clash with theirs. She prefers plain, sometimes muddy fashion choices over Rarity's lavish dresses, is more interested in rocks than Fluttershy's many animal friends, writes her own rock-themed poetry, and is honest to the point of bluntness. When the ponies tell Pinkie that they can't connect with Maud the way she has, Pinkie puts together a large obstacle course that incorporates all of their interests as a bonding activity. When Pinkie demonstrates how the course is run and inadvertently puts herself in harm's way, Maud springs into action and displays incredible speed and tremendous physical strength by smashing a giant boulder to bits. It's with this feat that the others realize the extremes Maud would go for her sister, and are able to befriend Maud over their shared love of Pinkie.
As Pinkie and her friends see Maud off and exchange rock candy necklaces, Maud smiles, saying that while she doesn't really like candy, she does love Pinkie Pie.