Amanda "Mandy" is the tritagonist of The Grim Adventures of Billy and Mandy. She serves as a main protagonist (though at times, antagonist). She is Billy's best friend and neighbor.
Unlike Billy, Mandy is a intelligent, insensible and sane. She appears to treat everyone around her with contempt, especially her friends, Grim and Billy—though, she does see Billy as a friend of sorts. She still has respect for some people, such as Nergal Jr., Hoss Delgado, Jeff the Spider, Pandora before being betrayed by her, the Unicorn and sometimes Grim.
Personality and Characteristics
Mandy is a cold-hearted, brutish, bitter, and behaves in a far more superior manner compared to most of the characters on the show. She aspires to dominate the planet with an iron fist and to stay as far away from Irwin as possible. Mandy’s antagonistic behavior had left her parents in shivering, fear and stay far from Mandy sometimes. Her mother showers her with money.
While Billy usually gets the trio into trouble, she is usually the one to get them out of it, along with Grim who—without her force—would not even bother trying to help. Billy claims she has an irrational fear of figure skaters, but she denies this by saying she "doesn't trust the way they spin is all." Mandy also has an intelligence and strength not to be reckoned with. She has an almost superhuman force as she is able to battle monsters with ease as well as being able to understand complex theories of the world when referring to her intelligence, despite being a child. She also never misses a chance to exploit the stupid, which more or less justifies her attachment to Billy.
Mandy is the main antagonist of the crossover episode The Grim Adventures of the Kids Next Door as she took over the Kids Next Door’s Moonbase.
When Mandy was a baby, she was been shown to have never smiled; even she was visibly unhappy in her mother’s womb. Her father stated in "Keeper of the Reaper" that wolves tried to take Mandy and raise them as one of their own when she was born. When she smiles, it throws off the natural order of the universe as seen in one episode, My Fair Mandy. Although, this does not apply in some earlier episodes, because she smiles only to her friends Billy and Grim. But she had to smile in front of everybody in the school auditorium.
In the episode The Problem with Billy, she first met her best friend Billy when they were in diapers. Billy had rung her doorbell several times until she was annoyed enough to answer. And Billy stole her feeding bottle, put in his mouth and flushing like a toilet. When she did, he immediately pointed out that she had no nose and shoved an ice cream cone into her face after she had asked him if he was “some kinda idiot?”. She punched him, called him a creep, and slammed the door in his face. He simply giggled in response to this, telling “she digs me”, thinking that she liked him. She and Billy had met Grim on the day of the tenth birthday of Billy’s pet hamster Mr. Snuggles in the first episode of The Grim Adventures of Billy & Mandy, Meet the Reaper. Grim had appeared to reap the soul of the hamster as it was time for the hamster “to kick the bucket” as Mandy had said earlier in the episode, but neither the hamster nor the duo would give in. So, they made a bet. If Grim was able to beat them in a game of limbo he would reap Mr.Snuggles' soul. However, if Mandy and Billy won, they would keep Mr. Snuggles as their pet again and Grim would be their best friend “forever”. However, Billy and Mandy had won –though not in a completely fair way—and Grim has been stuck with them since.