The Simpsons:
Season:     8     / Episode:     19    
Grade School Confidential

Seymour Skinner and Edna Krabappel strike up a conversation at a party and take a romantic interest in each other. They try to keep their affair a secret, but Bart sees them kiss. The following day the couple hears Bart telling his classmates about it and silences him by deleting his permanent records. Bart becomes their go-between for exchanging love notes, but he gets tired of that and exposes Skinner and Krapappel in the janitor's closet locked in a passionate embrace. The word spreads all over town and Superintendent Chalmers gives Skinner an ultimatum. Either end the relationship or face dismissal. Skinner admits that he is in fact a virgin and the matter is cleared up.