Maud Pie is a female Earth Pony, and older sister to Pinkie Pie.
Physical Appearance
Maud Pie shares a similar design to a number of female Crystal Ponies, including a singular eyelash. Her mane and tail are flat and even, similar to Twilight Sparkle. Her Cutie Mark resembles her pet rock, Boulder.
Her standard outfit is a dull blue dress with a dark grey belt.
Personality
Maud is often depicted with a blank neutral facial expression with her eyes half-closed and a dry demeanor that contrasts her more upbeat sister. She has a tendency to talk in a rather monotonous and dry tone of voice. She never smiles except for a few occasions while interacting with her closest friends such as Pinkie. In addition, Maud is shown to have a deep knowledge of and fascination with rocks. Despite her typically flat demeanor, she deeply loves her sister Pinkie Pie and shows a deep concern for her when her life is put in apparent danger. Despite not sharing Pinkie's interests in throwing surprise parties and making candy, she enjoys doing such activities with Pinkie solely because her sister does.
History
At the beginning of her debut, 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 Sparkle'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. 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, ignores Steven Universe's attempts for her to play with him and Blue, and is honest to the point of bluntness. As she and Pinkie walk through Ponyville, she sees Connie Maheswaran and Connie II together, her remarking that her parents must be missing them before going on.
When they 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.
Before she left for home, Maud says that Pinkie's lucky to have such special friends and left her with two friendship bracelets.
Abilities
As shown in her debut, Maud Pie is shown to have a high level of speed, endurance, and strength, capable of smashing a huge boulder into nothing but rubble in little time at all, to the point when it didn't even touch the ground. This is shown earlier when she tossed a rock over a lake, causing a "rock-splosion" afterwards.