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, it was revealed that Nurse Claiborne was responsible for giving the kids Pinkeye, using bacteria-infested water balloons, and that the toppings of her crumbles was, in fact, Pinkeye crust. When confronted, Nurse Claiborne shot herself point-blank in the face with her Pinkeye gun, completely covering her entire body in a shell of crust which then crumbled to dust, leaving no trace of the villain.
Ever since the KND told everyone at school about her Pinkeye Operation, Nurse Claiborne had been fired from her school nursing job and couldn't get another school nursing job in the country.
Nurse Claiborne returned in Operation: H.O.M.E., where she is revealed to be running the Rainbow Monkey Retirement Home, and making Rainbow Monkeys into breakfast cereal. She was defeated by Numbuh 3 and Numbuh 5 and then was forced to mend all 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 (who could rightfully be labeled as criminally insane if put into any remotely realistic context).