The Simpsons (1989): Season 21, Episode 2

21 - 2: Bart Gets a 'Z'

When Mrs. Krabappel confiscates student's cell phones, the class, organized by Bart, decides to teach her a lesson by spiking her coffee and watching her make a drunken fool of herself. Principal Skinner fires Mrs. Krabappel and replaces her with a cool new teacher, Zachary Vaughn, who impresses Bart and his friends with a hip attitude and love of texting, blogging and using Twitter and Facebook. Torn by his affection for Mr. Vaughn, yet plagued by guilt, Bart makes his way to Skinner's office to tell him the truth and get Mrs. Krabappel's job back. Blackboard: 'Chalkboarding is not torture'.