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.
Beverly Hills, 90210 (1990)
Episode list - season 6
More mistakes in Beverly Hills, 90210
Emily Valentine: This isn't Beverly Hills! It's Knot's Landing.
Trivia: James Eckhouse plays Jim Walsh, father of Brandon Walsh (Jason Priestley). In real life, Eckhouse is only 14 years older than Priestley.
Question: Was Valerie Malone introduced this season to balance out Brenda's departure?
Chosen answer: Yes, she was.