Gideon Charles Gleeful, or better known by his stage name 'Lil Gideon, is a self-proclaimed child psychic whose alleged visions have made him famous in Gravity Falls, Oregon. Gideon claims he can read minds, predict the future, and talk to the dead. His Tent of Telepathy is a competitor of Stan's Mystery Shack. Even though he seemed to have a rivalry with Grunkle Stan before, ever since the end of "The Hand That Rocks the Mabel," he has sworn revenge on the Pines family because he thinks they came between him and Mabel. Gideon also owns a warehouse, located at 412 Gopher Road. Gideon is arrested at the end of Season 1.
Gideon is first shown in an advertisement on the back of an issue of "Wacky News" in "The Legend of the Gobblewonker," with the words "Child psychic." After Soos shows the twins Gideon's commercial in "The Hand That Rocks the Mabel," they decide to test him as a psychic. They go to one of Gideon's shows, even though Grunkle Stan forbids them from going, due to Gideon often causing him trouble.
At the show, Gideon meets Mabel, and quickly develops a huge crush on her. He shows up at the Mystery Shack the next day, and asks her if she wants to go to his dressing room so they can do makeovers on each other. Mabel accepts the offer. Gideon then reveals he wants to be more than friends with Mabel; however, she doesn't feel the same way. He manages to convince her to go on a date with him. At the date, he convinces her to go on yet another date with him, after announcing it to everyone at the restaurant they were dining at. Mabel really didn't want to, but the many people in the restaurant expecting her to say "yes" put pressure on her and she gives in to him.
Dipper sees that Gideon has become a problem for Mabel and offers her the idea of him breaking up with Gideon instead of her, causing Gideon to believe that Dipper had come between them. Gideon gives Toby Determined Shandra Jimenez's phone number. In exchange, Toby calls Dipper, telling him to go to Gideon's factory. Gideon confronts Dipper there, and nearly kills him with his amulet. However, Mabel shows up to tell Gideon that she just wants to be friends, and she sees Gideon trying to kill Dipper. Mabel then formally breaks up with Gideon, and uses the amulet to defeat him, destroying it afterwards. Gideon is then seen fleeing into the forest, saying "this isn't the last you'll see of little ol' me."
Gideon makes his next appearance in "Irrational Treasure." He dresses up as a tomato farmer on Pioneer Day and teases Stan by throwing tomatoes at his eyes after Stan insulted Gideon by saying he looks less girly than usual.
In "Little Dipper," Gideon is playing with his Mystery Shack set, and decides that taking over the Shack would be the perfect way to get revenge. He first tries to get Stan to sign over the Mystery Shack, but Stan is not fooled. He tries to set termites on the Shack, but Stan smashes the jar and the termites go after Gideon's bat and his hair instead. After failing twice, Gideon discovers Dipper's crystal flashlight, which can grow and shrink things. He shrinks the twins and brings them back to his house. He calls Stan and tells him he has the twins in his possession, but Stan doesn't believe him. Gideon heads over to the Shack while Dipper and Mabel escape. Gideon catches them again and shrinks Soos, believing he was Stan. He then corners Stan in the Maze of Mirrors. Dipper and Mabel tickle his armpit, immobilizing him and allowing the twins to take back the flashlight. Stan then literally kicks Gideon out of the Shack.
Soon after, he paces around his house. His dad tells him he'll get his revenge one day, but Gideon angrily tells his dad that it's not just about revenge; he wants the Shack so he can find something.
In "The Deep End," he is seen at the local pool, taking the best spot right before Stan can get to it. Stan's efforts to get the spot back end in failure, even when he sneaks into the pool at night to sit on the deckchair until the pool opens; Gideon, having anticipated this tactic, reveals to Stan that he put glue on the chair.
In "Dreamscaperers," Gideon summons a mind demon by the name of Bill Cipher to enter Stan's mind in order to retrieve the code to a safe holding the deed to Mystery Shack. His plan fails, so Gideon resorts to Plan B; dynamite. He blows up the safe, takes the deed and has his father use a wrecking ball to destroy the Mystery Shack's sign.
Gideon plays a prominent role in the season finale, "Gideon Rises." He reveals the purpose of the journals, and tells his father (and the viewing audience) that he still requires the other one, 1. Upon stealing 3 from Dipper, however, he discovers that there are 3 journals and he pursues the Pines twins (who were forced to leave town around this time) in a giant robot under the assumption that Dipper kept the first one for himself. He catches them and attempts to reclaim Mabel as his bride and almost succeeds. He is stopped at the last moment by Dipper, however, and the robot crashes after a brief skirmish in the control center.
He attempts to have the Pines twins arrested, but Stan reveals the falsehood of Gideon's supposed powers: his special pins are hidden cameras. The scorned townsfolk turn on Gideon and arrest him, but not before Stan reclaims his deed and secretly steals 2 from Gideon in order to finish creating the machine in his secret laboratory.
When taken to court, he plans to use his "cute" act, but unfortunately for him Manly Dan is in the jury. He is then sent to jail. Fortunately for him, the inmates at the Gravity Falls jail love his psychic act and have been looking for a new leader. 
'Lil 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 times with Mabel.
He is cunning and sly, tricking Stan in "The Deep End" into getting glued to the deckchair. He speaks with a Southern American dialect. He is spoiled, ungrateful, bratty, selfish, and abusive toward his mother and father, such as throwing ice cream, yelling at them, making a fuss, and breaking lamps. His mother appears to fear him.
He can also appear very rude and obnoxious, an example is shown in "Little Dipper", where people are buying cars from his dad and he talks behind their backs, calling them "Mouth-breathing fools", and when he shrinks Mabel and Dipper.
He is enemies with Dipper because of Dipper getting in between Mabel and him. He is also enemies with the twin's Grunkle Stan, being a competitor towards the Mystery Shack.
He also seems to be completely obsessed with obtaining the power that the journals would give him, going so far as to attempt to track down Dipper and Mabel when they were leaving Gravity Falls and ignoring their claims to not have the first journal.He is extremely manipulative, lying to the residents of Gravity Falls to get them to do what he wants, such as telling them Dipper and Mabel blew up his statue with dynamite to get them arrested.
Appearance 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. He wore a jade amulet on his bolo tie until Mabel destroyed it in "The Hand That Rocks the Mabel". In "Irrational Treasure," it is replaced by a white tie. Also in "Irrational Treasure," he makes his hair curly to look like a "humble tomato farmer."
Shortly after his first encounter with Mabel, Gideon fell head over heels for her, and continually attempts to get Mabel to return the feeling through various schemes, but to no avail. Despite his crush, Gideon seeks revenge on Mabel and her family (whom he views as the only thing standing between a successful relationship). Mabel, on the other hand, finds Gideon to be creepy and unattractive, totally evil, and despises him and every attempt he makes to enact his vengeance.
For unknown reasons, a rival has existed between Stan and Gideon for years. Business rivals to begin with, their rather competitive personalities fuel their feud further. Gideon wishes to eliminate Stan for numerous reasons, namely to take control of his business and a strange secret it possesses and to remove the "obstacle" to winning Mabel's affection, and he plots day and night to figure out a means of revenge, though he is sometimes satisfied with simply irritating Stan. Stan doubts Gideon's abilities and constantly teases him.
Though a father traditionally has authority of his son, Gideon's and Bud's situation seems to be the complete opposite: Gideon bosses Bud around and Bud submits without a second thought. While Gideon just utilizes his father as a tool to help him reach his goals, Bud nonetheless loves his son and is willing to do much for him, seeing the boy as "precious." However, he is quoted as saying that Gideon "could use a time out" in article about Gideon's arrest.
Due to her son's sinister and intimidating nature, Mrs. Gleeful is submissive to Gideon and fears him, trembling at the mere sight of the young boy. Gideon lacks respect for her and treats her abusively.
Gideon's greatest talents are charm, deceit, and scheming. In "The Hand That Rocks the Mabel," he attempts to maim Dipper Pines using lamb shears after he "turned Mabel against him." Later in "Little Dipper," he formulates many plans to exact vengeance on the Pines family, ultimately leading to shrinking the twins to take possession of the Mystery Shack. He also once possessed 2, a prequel to Dipper's 3 that appears to contain mainly alchemical secrets, and therefore knew of and had access to many supernatural items, such as a Mystic amulet that gave him telekinesis (which was destroyed by Mabel) and cursed Egyptian super termites.
- Intro: "Gravity Falls theme song"
- 102. "The Legend of the Gobblewonker" (pictured)
- 104. "The Hand That Rocks the Mabel"
- 108. "Irrational Treasure"
- 111. "Little Dipper"
- 114. "Bottomless Pit!" (pictured)
- 115. "The Deep End"
- 118. "Land Before Swine" (pictured)
- 119. "Dreamscaperers"
- 120. "Gideon Rises"
- He is voiced by Thurop Van Orman, who also voiced Flapjack in the series The Marvelous Misadventures of Flapjack.
- 'Lil Gideon's appearance is based on Benny Hinn, a famous Christian televangelist who claims to be a prophet. He also bears a resemblance to child preacher Larry Hal Larimore.
- A picture of Gideon appears on a board in the Gravity Falls theme song.
- A variation of Bill Cipher can be seen on a paintbrush jar in 'Lil Gideon's room at the end of the episode "The Hand That Rocks the Mabel."
- Gideon's school ID number is 618, which is also The Mystery Shack's address and Alex Hirsch's birthday.
- In "Rumble's Revenge," a cryptogram references Gideon searching for an object of some sort, later revealed to be 1.
- Gideon is Hebrew for “destroyer” or “feller of trees,” which is fitting considering his archnemeses are the Pines Family.
- The reason why Gideon's skin is so soft is because he steals Wendy's moisturizer.
- Gideon has been to summer programming classes.
"Hello, America! My name is 'Lil Gideon!"
"People have a hard time saying 'no' to me."
"Dipper Pines, you don't know what you've done! You've just made the biggest mistake of your life!"
"I can buy and sell you, old man!"
"This isn't over. This isn't the last you'll see of 'lil.... ol'.... me...."
"Finally after all these years, after every humiliation! Your business, your family, everything will finally be mine! You have no one to protect you now!"
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