The character of Dylan was only supposed to appear in eight episodes. Fox executives weren't sold on the fictional character or Luke Perry's acting ability. Aaron Spelling used his own funds to pay Perry's salary during those initial episodes, and the positive audience response led Fox to approve his addition to the regular cast.
The series took a while to find its audience, and it didn't find much of one at all in the first season. On the still very young Fox network, the first season finished the 1990-91 season ranked #118 of all shows, trounced in its Thursday night time slot by NBC's Cheers (1982). But Fox executives had a novel idea - instead of going into reruns in the summer of 1991, new summer-set episodes were produced and aired. Up against endless reruns on the other channels, the show found a lot of viewers, which stayed with the show into the new fall season. They went on to produce more summer episodes in 1992.
In its early seasons, the episodes were issue-based, until the producers decided it should be a teen soap opera.
At time the series premiered, Shannen Doherty was 19, Jennie Garth was 18, Tori Spelling was 17, Jason Priestley was 21, Luke Perry was 23, Brian Austin Green was 17, Ian Ziering was 26, and Gabrielle Carteris was 29.
The show's success was due to the ending of the Gulf War. The teen drama actually began as a family show centered around the Walsh family, but shifted focus on Brandon and Brenda's high school friends halfway through season one. The first of these teen-centered episodes aired in February 1991, on the same day that every other network had suspended programming to report on the Gulf War. Fox didn't have a news department at the time, so it aired 90210 and got a ratings spike due to the lack of competition.