Shannen Doherty in 1990

Shannen Doherty: Then

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Though Doherty was an O.G. cast member as Brenda Walsh, she was written off the show after four seasons. Doherty was notoriously difficult on set and there was an infamous on-set feud between her and co-stars Tori Spelling and Jennie Garth. Years later, Spelling admitted that she got the actress fired from the teen soap -- her father, after all, was 90210's creator and producer, Aaron Spelling.

Shannen Doherty in 1990