Ms. Knickerbocker (voiced by Candi Milo) is head of Sheffield Institute. She is disliked by almost all the students there, and is thought of uncool, like when she tries to rap the morning announcements. Knickerbocker is fairly strict, but she is fair. She thinks high of the W.I.T.C.H. girls but low of Uriah and his gang. In the first season, she dealt with Rick Hoffman (Cedric's alias) a lot in development of the school, resulting into some problems. She became a Trance Marcher in "Walk this Way". In the second season, she finds herself having to put up with the W.I.T.C.H. girls especially Will and Taranee due to problems occurring through Nerissa the Guardians having to break rules to protect Earth.
In issue #114, it's discovered that her first name is Katherine and is the daughter of one of the previous Sheffield headmasters.