The College of Crooks (known as The Owl, The Rattler, Hurricane Harry, Jack-in-a-Box, Dr. Madcap and his wife Greta Ghoul) are a group of Cool McCool's enemies who appear each of their own episodes until together at the last episode.
- The Owl: An owl-themed elderly supervillain who is the main and primary antagonist of the Cool McCool series. He lives in a cave, sports female owl henchwomen, and has owl pets. He is the first villain that Cool McCool encounters in the series and he is always seen walking bare-footed. He is the headmaster of the College of Crooks, which was McCool's old college being turned as a secret hideout. He is a parody of The Penguin. He is voiced by Chuck McCann.
- The Rattler: A green anthropomorphic snake with a passion for the arts. He has the ability to control plants and also adores plant life. He can even communicate with the plants and treats them all with care. He can also wield shotguns and bombs. His catchphrase is "seize him" which is mostly used when he orders his plants to capture McCool. Because of his human appearance (except skin color), he can easily pull off a disguise when taking rare art. He also shares the same features and instincts as a snake as he hisses and falls for the snake charmer. He is the Professor of Body in the College of Crooks. He is a parody of The Riddler. He is voiced by Chuck McCann.
- Dr. Madcap: A wacky supervillain with the ability to control any hat and make them do his dirty work. Although he adores his hats, he also loves Greta Ghoul, his wife, who is sad since he spends more time on the hats than her, so he commands the hats to give Greta presents to make her happy. He is a parody of the Mad Hatter. His characteristics are similar to his parodied counterpart as he is brilliant but also psychotic as well. His hats sometimes lead many surprises such as anvils or guns. He is the first professor of science in College of Crooks. He is voiced by Chuck McCann.
- Greta Ghoul: Dr. Madcap's wife. She doesn't feel much appreciated or loved by her husband in some episodes and speaks with a Transylvanian accent. She is a green color-schemed woman who is often moody and depressed. Like her husband, she is myopic. Hench her name, she can be seen popping out everywhere in a blink of an eye, mostly on pots. She is the second professor of science in College of Crooks. She is voiced by Carol Corbett.
- Hurricane Harry: An overweight supervillain who can create mighty gusts of winds to blow many things away from his path. He speaks in a deep voice and a lisp. He lives with his fiancée Bellows Belle, who wheezes when speaking. It seems that he regrets his powers or he gained his powers by accident when he was young because in his first appearance when he was blowing out the candles of his birthday cake and it blows the whole cake away, he cries out "Every time!" meaning that his powers have ruined his birthdays because he is unable to blow out the candles properly due to his wind power. Unlike the others, he is a parody of most criminals under the name Hurricane in the Marvel Comics. He is the Professor of Physical Education in College of Crooks. He is voiced by Chuck McCann.
- Jack-in-a-Box: A supervillain wearing joker attire that hides in a jack-in-a-box to scare and attack people. His weapon is his shotgun and a bomb. His residence is in a multi-colored jack-in-a-box, possesses a Magic Mirror who is actually an exact clone of himself and his pets are lions. Whenever he talks, he says a sound or word that are similar to that of jack-in-a-box sound effects and or music (like popping out sounds). His movements and stature are always in motion when he speaks, making his waist going up in down like he's popping out, and his voice vibrates. Most of his attacks would evolve explosives and guns. He is the college cheerleader in the College of Crooks. He is a parody of The Joker. He is voiced by Chuck McCann.