Chester is a man who has been seen conducting various money-making operations at the expense of children. Unlike most other villains, Chester's character and actions lack a consistent "theme" and vary wildly between his appearances, aside from his greed.
Chester is a large man with a round nose and a thick brown mustache. His attire can be various being with many disguises. His overall attire is that of a scientist's long coat.
He is ruthlessly greedy and evil towards kids, and sometimes tries to use them in his money-making schemes. He is also a proclaimed genius scientist creating different kind of inventions just to put kids in misery.
He first appeared in Operation: C.A.M.P., in which he is the councilor of "Camp Lemmeouttaheah", where kids were brainwashed into making wallets and lanyards for Chester to sell. With the help from their new teammate Bradley and his parents, the KND defeated Chester and set the campers free.
In Operation: F.A.S.T.-F.O.O.D., Chester enacts what is undoubtedly his most despicable plan ever (and possibly the most gruesome operation of any villain in the entire series): opening a fast food restaurant called Burger Frenzy, where kids visiting the restaurant are captured and used as the meat on burgers which are then sold to sharks. This horrific plan was stopped by Kuki during her birthday "mission" of picking up lunch.
In Operation: U.T.O.P.I.A.., Chester creates the "Happy Headband", which traps the victim in a virtual reality in which they experience a personal paradise. However, the device can be adjusted to turn the dream "sour". He intended to sell it to parents as a product designed to keep children under control. The Happy Headband was tested on Nigel Uno, who eventually escapes using the jet boots he is wearing in real life. He then puts the Happy Headband on Chester. In Chester's fantasy, he has defeated Numbuh 1 and finds himself in a room surrounded by a cheering crowd of his fellow villains. Mr. Boss then awards Chester a check for "a buhmillion dollars" for his victory. At the end of the episode Wallabee turned the dial to Sour at which point Chester realized that he was wearing his own headband.
In Operation: S.A.F.A.R.I., Chester disguises himself as "Dr. Phineas Sharp", a doctor who gives vaccination shots for "Moosebumps". he used Nurse Jumbo, a needle-hating elephant who quittted working for Chester after receiving repeated vacinations by mistake due to Chester's poor aim and Nigel Uno's quick foot work. However, the shots he gives actually cause Moosebumps, which literally turns the victim into a moose. Chester intends to saw off the antlers of his victims and use them to make "Chester's Marvelous Moosicles". Though at the end of the episode it's revealed the entire episode was the paranoid ramblings of Nigel Uno who was trying, and failing, to explain to his mother why he shouldn't get his moosebumps shot, in the final shot of the episode it's revealed that Chester is the secretary for the real doctor.
- Earlier drawings of Chester show that he was going to be based on a moose, with moose antlers. This idea was redesigned into the plot of Operation S.A.F.A.R.I.
- He is one of the few villains in the series to have a practical motivation for villainy other than harming children.
- Unlike other villains in the series who mainly target rebellious kids such as the KND, Chester is perfectly willing to target completely innocent children.
- Two of his appearances involve him getting into a one-on-one duel with Numbuh 3.