The Majestic Twelve (マジョスティック・トゥエルブ), also known as MJ12, is a league of American superheroes apparently led by Dr. Riddles. They are seen at various points in the series, and although they seem to have great powers, they are mostly shown as humorously incompetent at fighting, preferring to use riddles and confusion to defeat their opponents (though this is only in the anime; there is no indication in the manga that their powers are not all they are portrayed as). The Majestic Twelve are shown to have a certain degree of respect for Dr. Riddles, which is demonstrated when they try different ways to cheer him up after Kid's book is burnt (though all plans fail miserably). They are named after the purported secret committee of American scientists that supposedly investigated UFO incidents in the Truman era.
- Lightning Eye (ツー・ライティング・アイ Two-Lightning Eye in the Japanese version), who shoots lasers from his eyes (actually can only shoot light, which has no effect at all);
- Rocket Foot (ロケット・フット), with a top speed of 300 km/h (but gets tired easily);
- Flying Beat (フライング・ビート), able to soar the sky (but cannot steer properly);
- Second Sight (セカンド・サイト), a man with clairvoyance (but can't really do anything with his powers);
- Dinosaur Arm (ダイナソー・アーム), with the strength of a dinosaur (as well as the intelligence of one);
- Future Wonder (ワンダフル・トゥ・ザ・フューチャー Wonderful to the Future in the Japanese version), who can see into the future (which doesn't help in battle);
- Psychic Jungle (サイコ・ジャングル Psycho Jungle in the Japanese version), a wild barbarian with telekinesis and telepathy (but frequently gets distracted by girls, remarking "You're pretty..." while drooling);
- Fire Elbow (ファイアー・エルボー), who can use pyrokinesis (but has no control over his abilities);
- Lady Susan (ビッグ・ボイン Big Boing in the Japanese version and the Youtube Dub), who smells nice (a bit like lavender, which isn't really a power). Her Japanese name refers to her oversized breasts; her power involves bouncing them up and down or batting them with her arms to distract everyone. She is the most prominent of the twelve, appearing occasionally on her own and consistently seen alongside Dr. Riddles. She also, on occasion, is shown as actually able to fight. Her dialogue consists almost exclusively of the word "Yeah".
- Blizzard Thing (ブリザード・シング), a youth who can use cryokinesis (and like Fire Elbow cannot control it);
- Tremor Mole (トレマー・モグラー), who can travel freely through the ground (but cannot see underground so constantly crashes);
- Telepathy Radar (テレパシス・レーダー) who commands them all and enhances their powers (however most of the others have been defeated before he can help at all). He is also the pilot of the plane used by Sunbeam and Ponygon as they rush to take on one of Clear's minions at the time of the final battle.