Other mistake: When the show aired in 1990, in the pilot episode Brenda falls for Jason. She later on reveals herself to be a "16 year old junior" in high school. Season 2 opens up with the gang on summer break which technically would make them going into their senior year. It wasn't until Season 3 that they were going into their senior year. They graduated in 1993 from West Beverly but the show debuted in 1990 so technically they should have been sophomores.
Deliberate mistake: The layout of the Walsh house, both interior and exterior, is different in the pilot than it is in the rest of the series.
Answer: The students were told by the faculty that anyone found to be intoxicated at the Senior Prom would not be allowed to participate in graduation activities. Donna had a little too much champagne at Mel's house and in the limo and got drunk. At the Prom she spent most of the time in the bathroom, being sick. As the gang tried to discreetly usher her to the car, Donna fell and Mrs. Teasly questioned her and realized that she was drunk. "Donna Martin graduates" is what her classmates chanted after a walk-out on their final exams, in protest to the fact that the board was meeting inside to make the final decision of Donna's fate. Big surprise: Donna Martin graduated.
elleemann