Dr. Sigmund Teef is a dentist who who works in an office near Jelly's Candy Store. Dr. Teef only appears in Operation: T.E.E.T.H.. His surname is a pun on the word "teeth". He is first seen offering the members of Sector V a free checkup, but is rudely shrugged off, much to his displeasure. After encountering Knightbrace, the KND assume the villain to be Dr. Teef. Knightbrace is eventually revealed to be Mr. Jelly, the owner of the candy store, and Dr. Teef ends up saving the kids by using a rope of taffy (Knightbrace's delicious weakness) to disable the Dental Assault Chair. After Knightbrace is defeated, Dr. Teef tells the kids that his "lazy brother-in-law" will be put in charge of the candy store and again offers them free checkups, but the offer is again refused.