Toiletnator: Lou Pottingsworth III is a pathetically weak and incompetent antagonist (being considered the lamest villain in the KND world and absolutely no threat at all). He's a Toilet-themed super villain who is disregarded as a threat by the KND and considered an embarrassment or liability by other villains, in part due to his ridiculous (even by KND villain standards) motif. 

Knightbrace: Mr. Jelly a.k.a Knightbrace is an oral health-themed villain who attacks children at night and forcibly performs painful and unnecessary dental and orthodontic procedures on them.

Stickybeard: Stickyfuzz is a candy-loving pirate who sails around the suburbs where the members of Sector V, live in his ship: the Sweet Revenge. Along with his crew of Candy Pirates, Stickybeard hoards candy in the same manner that traditional pirates horde gold, and gets the candy primarily by stealing it from various children. 

Gramma Stuffum: A fat old lady obsessed with force-feeding her disgusting food to children to fatten them up, believing that a child that is too fat to move can't get into trouble. She also speaks with a German accent.

Common Cold: An eternally ill villain who wishes to spread his cold to everyone else in the world. He uses a machine to fire mucus from his nose at his enemies. He can routinely be defeated with orange juice.

Count Spankulot: A vampire who exists to spank naughty children who have violated rules. He appears to his victims in a terrifying way and announces their crimes and his name before he proceeds to punish them. Count Spankulot also speaks with a deep Romanian accent.

Cree Lincoln: She is the older sister of Abigail Lincoln. She is currently 16 and is leader of the Teen Ninjas in service of Father. Cree was a KND operative under the codename of Numbuh 11 in Sector V before she turned 13, at which point she escaped decommissioning and defected to the side of evil. It was from Cree that Numbuh 5 learned many of her fighting skills & abilities, but the two are now arch-enemies.

Delightful Children From Down The Lane or (DCFDTL): They are so bent on the destruction of the Kids Next Door Organization and the supremacy of adults over children. The DCFDTL speak in synchronization and stand together in group formation. Their names are Bruce which is the short blond boy, David is the tall brunette boy, Lenny is the boy in the helmet, Constance is the short dark brown haired girl, and an unnamed blond girl that has a pink bow.

Father: His ultimate goal is to destroy the Kids Next Door so that the adults can rule the world unopposed. His body is completely black with a red outline along his body and eyebrows, giving him a silhouette-like appearance with few other discernible features, the most notable among them being his bright yellow eyes, which often are exaggerated since his eyes are the only way of visually seeing his facial expression and his mouth is rarely ever visible.

Mr. Boss: A corrupt, child-hating, corporate executive who acts as the de-facto leader of the KND's standard rogue's gallery.