Gideon Gleeful is a fraudulent child "psychic" whose hunger for ultimate power motivates him to manipulate and intimidate others into giving him what he wants.
A sworn enemy of the Pines family, he becomes the Mystery Kids' enemy in the process as well. Raz and Lili have a particular hatred towards him for being a fake psychic due to them being actual psychics.
Gideon, despite being ten, possesses knowledge of the supernatural on par with Dipper and the rest of the club. This makes him even more dangerous as he is able to use paranormal beings and objects to destroy the Mystery Kids and more importantly the Pines family. This hatred towards the family and the Spook Crew often warrants Gideon into taking extreme measures to get rid of them, such as making a deal with dangerously powerful entities like Bill Cipher or Giygas.
Gideon is a short, stout kid with white pompadour hair bigger than his head. He has an upturned nose, blue eyes and three freckles on each of his cheeks. He wears a baby blue suit, a black shirt, and an American flag pin on the left side of his collar, with brown, polished shoes.
Gideon is a self-proclaimed television psychic whose real mission is to take down his competition, the Mystery Shack. He uses his "cuteness" as an advantage to get what he wants and admits that people have a hard time saying "no" to him because of it. It seems that he can be kind when he needs to be, as seen with most of his dates with Mabel.
He is spoiled, ungrateful, egotistical, selfish, and abusive especially toward his parents in ways such as throwing ice cream, yelling at them, making a fuss, and breaking lamps. He's also very vengeful, even to the point of trying to murder the Pines family and the rest of the kids after being rejected by Mabel once again and losing the debate to Stan. Though he is naturally mischievous, after Gideon is corrupted by Giygas, his childish sense of humor becomes increasingly malicious.