You could almost do an entire article about the many forgotten subplots in Lost alone. I particularly like their write-up of the Tori Scott episodes of Saved by the Bell

When NBC ordered more episodes of the show’s already-wrapped senior year, Tiffani-Amber Thiessen and Elizabeth Berkley were already committed to other projects. So, employing its signature logic, Saved By The Bell allowed the characters to disappear completely, bringing in Leanna Creel’s motorcycle-riding tomboy Tori to replace them—and thus creating the “Tori Reality,” a parallel universe centered on Zack and Tori’s awkward courtship, a place where Kelly and Jessie simply did not exist.