Shannon Doherty and James Woods.
Shannon was fired from Beverly Hills 90210 due to conflicts with Aaron Spelling. Also fired from Charmed by Spelling. Both firings due to her bitchy and demanding attitude and treatment to everyone. She also was fired from Scare Tactics for the same reasons.
James Woods said in an interview that he's an asshole and treats everyone the same: like they are shit. He admits he's a jerk, but I think he's a great actor and I can live with his attitude.