Nurse Claiborne is a recurring villain who was once a seemingly benevolent nurse at Gallagher Elementary School who was known for her delicious crumble pastries. Her schemes often involve cooking and selling delicious foods containing various scretions obtained from her patients.
In Operation: P.I.N.K.-E.Y.E., when the students of the school began falling to a mysterious epidemic of Pinkeye and Numbuh 2 investigated the case, he discovered that Nurse Claiborne was responsible for giving the kids Pinkeye, using bacteria-infested water balloons that her hired associate Joe Balooka helped to use against the students. Not only that, but it was revealed that the topping of her crumbles was, in fact, Pinkeye crust, and that she was secretly harvesting it from her victims to increase her profits at local bake sales. When Numbuh 2 confronted her, she gained the upper hand until Joe, whom she had betrayed and shot when he was about to reveal who hired him, shoots her back, buying Numbuh 2 enough time to call the rest of Sector V for reinforcements. In a last ditch effort, Nurse Claiborne claims that they'll never take her, and shoots herself point-blank in the face with her Pinkeye gun, covering her entire body in a shell of crust which then crumbled to dust, leaving no trace of the villain. Immediately afterward, Numbuh 2 spotted her running through the rafters to escape, saying that he hadn't seen the last of her.
Afterwards, the KND revealed to everyone the truth of her Pinkeye Operation, resulting in Nurse Claiborne losing her job and having no success in gaining another one anywhere in the country.
She eventually returned as the main antagonist in Operation: H.O.M.E., where she is revealed to be running the Rainbow Monkey Retirement Home, a front used for making Rainbow Monkeys into Rainbow Munchies cereal, which significantly improved the taste. Numbuh 3 and Numbuh 5 uncovered her plan and defeated her, and then forced her to mend all of the Rainbow Monkeys back together.
On the surface, Nurse Claiborne seems to have a very kind and nurturing personality, which ultimately proves to be a front for her ulterior motives. In reality, Claiborne is a cruel, greedy, opportunistic woman who sees her patients as tickets to fortune, acclaim, and revenge. Also, despite her position as a heath care provider, she's certainly not above feeding something as unsanitary as human eye crust to unsuspecting customers.
Nurse Claiborne has a very stocky figure with very bulky chest and a cleft in her chin. She wears a shade of pink lipstick, and has her hair done up in a bun with a green hairband. Nurse Claiborne's uniform consists of a white, buttoned up medical coat with roped-up sleeves and two vertical grey stripes that start at the point of her lapels. In addition, she wears a white nurse's cap with a horizontal green stripe, a green cape, brown loafers and a pair of medical latex gloves. After being hit with a water balloon, the left side of her face is permanently scarred with pink-eye crust. She's been know to use two separate weapons: a 2x4 tech water balloon launcher and a red handgun with white nurse crosses printed on the sides and sight that fires enormous band-aids.
- Nurse Claiborne is one of the only villains who is portrayed as insane within the universe of the show, and her actions are played more seriously and realistically than the rest of the KND's rouges gallery although the only other one who did something more crazy than her and every other villain was Chad Dickson when he tried to send The Moonbase into the sun which basically meant he tried to murder children.
- She's one of the few recurring villains who isn't seen attending the usual villain gatherings.
- She is a parody of Sweeney Todd's original portrayal in The String of Pearls