ER: Season 06 (1999)

The impossibly obstreperous Dr. Robert Romano (Paul McCrane) matriculates from recurring to regular character as the Chicago-based hospital drama ER enters its sixth season. Other incoming cast members include Maura Tierney as OB nurse Abby Lockhart, who is introduced when she delivers the twin babies of Nurse Carol Hathaway (Julianna Margulies); Goran Visnjic as troubled Eastern European émigré and war veteran Dr. Luka Kovac, Erik Palladino as zany Dr. Dave Malucci; and, back after a lengthy absence, Ming-Na as former intern and now full doctor Jing-Mei "Deb" Chen, who in her med-student days had been a formidable competitor to Dr. John Carter (Noah Wyle). Conversely, a number of familiar characters make their exits this season, most notably George Clooney as maverick Dr. Douglas Ross and Julianna Margulies as long-suffering Nurse Carol Hathaway; the season's penultimate episode, detailing with the ultimate fates of Ross and Carol, is among the series' most famous sequences -- and one which was surprisingly kept secret until the very night of the telecast. Additional "defectors" include Gloria Reuben as HIV-positive Jeanie Boulet, who has gotten over her earlier romance with prickly Dr. Peter Benton (Eriq La Salle) and has wed police officer Reggie Moore (Cress Williams); and Kellie Martin as med student Lucy Knight, who is stabbed to death by a deranged patient, an attack that also seriously imperils the life of Lucy's erstwhile lover Carter -- who even upon recovery endangers himself by turning to drugs. Season five plot developments include Romano's ascension to chief of staff, a promotion given as part of a deal whereby Dr. Kerry Weaver (Laura Innes) would be appointed ER chief; Romano's subsequent and surprising appointment of his verbal sparring partner Dr. Elizabeth Corday (Alex Kingston) as his assistant; Corday's blossoming romance with her colleague Dr. Mark Greene (Anthony Edwards), and the reciprocal love affair between Corday's mom and Greene's dad (who dies later in the season); Benton's affair with Dr. Cleo Finch (Michael Michele), counterpointed by his incessant squabbling with his sister Jackie (Khandi Alexander); and guest star Alan Alda, who in a poignant story arc plays a celebrated surgeon in the first stage of Alzheimer's. The traditional season-ending cliffhanger finds Carter facing a crucial decision: seek out treatment for his ever-growing drug dependency or destroy whatever career he has left. ~ Hal Erickson, Rovi