Wears a yellow trench coat and sports a versatile mustache that tingles at the approach of danger and doubles as a telephone to call Number One. Despite fancy gadgets and a flying Coolmobile, Cool usually wins through sheer dumb luck rather than competence. He also has catchphrases such as "Danger is my business!", "When you're right, Number One, you're right", and "That will never happen again, Number One!" He has a distinct, jet-black pompadour hairstyle with a prominent swirl or wave at the top front, paired with thick sideburns. He has large, expressive eyes with heavy eyelids that often give him a tired, deadpan, or skeptical expression. He possesses thick, dark, and expressive eyebrows that sit high on his forehead. His most iconic trait is a thin, black, pencil-style mustache that juts out horizontally past his cheeks. This mustache doubles as a communication device and tingles whenever danger is near.

His face is never shown onscreen; viewers only see his arms, a chair, and a lit cigar. He has zero patience for Cool’s literal klutziness. Whenever Cool brings an assignment to a chaotic, destructive end inside the office, Number One instantly reacts with irritation, reaching for the dashboard on his desk to mechanically eject Cool from the room. However, his anger evaporates the second Cool is gone. Despite Cool's absolute incompetence, Number One harbors a genuine, almost parental fondness for him. His signature, defining catchphrase is a cheerful, chuckling "Hee-hee-hee, love that boy!" which he delivers after punishing Cool. As leader of the Secret, Inc., he takes global threats seriously. He expects perfection, demands compliance.

One of the members of the College of Crooks. He is a green, human-like, anthropomorphic snake. He has human-like proportions including arms and legs, which allows him to easily put on disguises when he attempts to steal rare artwork. He considers himself a sophisticated criminal with a passion for the arts and an adoration for plants. He creates mobile, plant flunkies to do his work and often uses the catchphrase "Seize him!" when ordering his partners to attack McCool. His deep snake instincts cannot resist snake-charming music, making it his weakness.

Jack-in-the-Box is a cackling, eccentric criminal who views high-stakes theft as a game. He loves spooking his victims and pulling pranks, such as posing as a photographer to swipe a diamond necklace. He lives up to his name literally; his body operates like a coiled spring. Whenever he stands or speaks, his waist and torso constantly bounce up and down in a rapid "popping out" motion. He often hides inside, jumps out of, or travels within oversized, multi-colored jack-in-the-boxes to startle people and execute robberies. His speech pattern matches his physical bouncing, his voice heavily vibrates and wobbles, and his syllables sound like a spring stretching out. He often peppers his dialogue with a wobbly laugh: "Arh-arh-arh!" a member of the College of Crooks. But his body functions like a coiled spring and he relies entirely on spring-loaded weaponry, jamming his mechanical toys is one of his weaknesses.

Husband of Greta. True to name, he has a distinctive mad scientist look capped off with an oversized, tall top hat or varieties of wacky headwear. He wears thick, round glasses, and like his love interest, he is myopic. is completely obsessed with headwear and possesses the bizarre ability to control any hat. He uses hats to do his dirty work. He is a member of the College of Crooks. Knocking off his headwear or glasses is his weakness.

A member of the college of crooks. He is an overweight, stout human villain. He has a wide mouth and puffed-up cheeks designed to hold massive amounts of air True to his weather theme, Harry has a very boisterous, deep voice but speaks with a lisp. His most defining facial feature is a prominent, oversized buck tooth that sticks out of his mouth, however, his buck tooth is like his Achilles' heel, If his tooth is knocked out of his mouth, he loses all his lung power.

Wife of Dr. Madcap and member of the College of Crooks Greta is a depressed, light gray or green-skinned woman modeled after a ghost or vampire. She serves alongside him as the Second Professor of Science. When she and Madcap get romantic, Madcap seduces her by whispering ridiculous, empty "sweet nothings" into her ear such as: "Your eyes are like nothing! Your lips are like nothing!" to which Greta dreamily replies, "I love you, darling—you're all evil!" Her extreme vanity is her greatest weakness.

An elderly human villain with physical traits that heavily resembles an owl. He has a sharp, beak-like nose, massive round eyes hidden behind glasses, and tufts of gray hair on the sides of his head that mimic owl feathers. His most unusual physical quirk is he always walks bare-footed, but attacks targeting his exposed soles is his weakness. Headmaster of the College of Crooks.

Friday is the secretary to Number One and has an unrequited crush on the secret agent Cool McCool, McCool remains oblivious that she crushes on him. She has a notably dowdy, unglamorous appearance. She is shorter, stocky and more stout compared to the tall, lanky and slim McCool.