Dr. Sigmund Teef
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.
- This character's name may be a spoof of the character Dr. Teeth from The Muppets.
- Dr. Teef is the first adult to render aid to the Kids Next Door.
- When Dr. Teef says, "But we told you in school...," this is evidence that he knew Mr. Jelly in dental school. However, it's not clear of whether he was a classmate or teacher.