Nurse Claiborne was a seemingly benevolent nurse at Gallagher Elementary School who was known for her delicious crumble pastries. 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, and that the topping of her crumbles was, in fact, Pinkeye crust. 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. Hearing him say this, 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.
- 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.
- She is a parody of Sweeney Todd's original portrayal in The String of Pearls