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Twenty years ago this week, a little hospital show called ER debuted on NBC to much fanfare and managed to exceed the hype. For years, it was television's #1 drama; it reinvented the television form, bringing a previously-unseen cinematic approach to shooting action in its Chicago hospital setting. And it had one of the deepest, craziest, most lovable ensembles in the history of television, both helped and eventually done in by its excessive longevity. There are so many characters in the history of ER that of course it'd be impossible to rank them all in any kind of definitive way. What's that? Someone's done it? He must have been mad to approach such a task single-handedly. Below follows a ranked consideration of ER's cast, including any recurring hospital employee who made an impact; briefer guest stints were not considered, and neither were peripheral characters like family members.

1. Carol Hathaway (Julianna Margulies)

(Seasons 1-6, Guest Star in Season 15) Of the original cast, who dominated the show for its first eight seasons, Hathaway emerges the most beloved hero. She attempts suicide in the pilot episode and was originally intended for death, but audiences responded well enough to Margulies for NBC to decide to keep her around. Hathaway was the beating heart of the show, whose romantic tribulations and career struggles (she thinks about going to medical school and decides against it) defined the soapier, serial side of the show more than any other main character. And of course she gets the best ending, walking into the sunset with Doug Ross, and dropping back in with him for the last season to show us how well they were still doing.

2. Peter Benton (Eriq La Salle)

(Seasons 1-8, Guest Star in Season 15) Probably the most divisive of the original cast, but count me in as a huge fan. Benton was a driven surgeon, desperate to achieve success at the cost of personal friendships or long-term romance, but he was a good guy behind all those grumpy forcefields. His relationship with John Carter, a former mentor and eventual peer, was one of the best in the series, and any time his serious façade cracked, it'd make the episode.

3. Doug Ross (George Clooney)

(Seasons 1-5, Guest Star in Seasons 6, 15) He starts out as a stereotype—the wildcat maverick, drunk and handcuffed to a hospital bed, sleeping with assorted women to evade some darker internal demons. But Clooney immediately elevated the material he was given and made Ross complex but still lovable—he was never quite trustworthy but you were always on his side anyway. It's kind of amazing he stuck around the show as long as he did (Clooney left in 1999, the same year Three Kings came out) but his performance, as great as it always was, wasn't bogged down in movie-star wattage. Ross felt as fully-realized and relatable as any of the original cast.

4. John Carter (Noah Wyle)

(Seasons 1-11, Guest Star in Seasons 12, 15) If you're just counting the early seasons, Carter might be atop the list. It's hard to remember what a goofy, fun, pratfally presence Wyle was in the first years of ER, playing the original viewer-surrogate character—the student entering County General for the first time and learning the ropes of trauma medicine. Carter's problem is that in later years, when the torch was handed to Wyle, things got excessively dramatic and the character was bogged down by drug addiction subplots, and later his trips to Africa, which always had a didactic tinge to them. Fun Carter was the best; no-fun Carter was a seriosuly cut-rate Mark Greene

5. Mark Greene (Anthony Edwards)

(Seasons 1-8, Guest Star in Season 15) The show's original protagonist, Greene is easy to love despite his many flaws. He's far too serious, always weighed down with personal angst, be it his disintegrating marriage, his crush on Dr. Lewis, his PTSD following a mysterious assault in a County bathroom, his ill-advised second marriage to Dr. Corday and finally his brain cancer. Edwards was such a charming actor that he managed to keep you on Greene's side even as things got more and more melodramatic, but by the time the show dragged out his death (over three episodes!) it was clearly time for him to exit.

6. Kerry Weaver (Laura Innes)

(Seasons 2-13, Guest Star in Season 15) A groundbreaking character (one of the first three-dimensional lesbians on TV) who constantly refused to be defined by any of the labels you could affix to her—she was disabled, walking with a crutch, and adopted, sometimes searching to reconnect with her birth parents. More importantly than anything, Weaver was an abrasive and domineering, career-minded doctor who came into conflict with just about every character on the show at one point or another, but never at the cost of your overall sympathy for her.

7. Robert Romano (Paul McCrane)

(Seasons 4-10) The man we all loved to hate! Right? I guess some people just hated him. Romano was an unrepentant jerk—sexist, homophobic, overwhelmingly obnoxious and pathologically obsessed with being in control. He served a valuable purpose in the early years as someone who would go to war with similar control-freak Dr. Weaver; he could also deflate the tension of any dramatic moment with a well-aimed offensive remark. Romano wasn't for everyone, but he bolstered the dull middle seasons of the show; his death, by helicopter, is probably the clearest point at which the show jumped the shark.

8. Greg Pratt (Mekhi Phifer)

(Seasons 8-15) If I had to pick a character from the later seasons of the show, it'd certainly be Pratt. A smart, cocky, unpredictable Ross clone in early seasons, he eventually matures into one of the reliable authority figures of the closing seasons of the show, although of course he gets mixed up in all the same ridiculous drama as everyone else (ER really ran out of plausible ideas when its seasons got into double-digits). Phifer is an incredibly likeable actor and had one of the more normal romances of the latter seasons (with Chen); he died under absurd circumstances at the start of season 15.

9. Elizabeth Corday (Alex Kingston)

(Seasons 4-11, Guest Star in Season 15) One of the first and more controversial additions to the cast, Corday was easy to love (wisecracking Brit with no tolerance for fuddy-duddies!) but got mired in boring drama when the writers decided she should hook up with, and quickly marry, Dr. Greene. Their all-consuming boring relationship aside, Corday was a very reliable spark-plug in the middle seasons who probably never should have stopped dating Benton (a romance that was nixed because La Salle eventually objected to it).

10. Haleh Adams (Yvette Freeman)

(Recurring in Seasons 1-15) ER had a reliable cast of background nurse actors with distinct personalities, although they rarely got major storylines to play around with. Haleh is probably the most memorable of them all, and was guaranteed to know what to do better than 95% of the people she was in a room with at any time.

11. Luka Kovac (Goran Visnjic)

(Seasons 6-14, Guest Star in Season 15) The designated successor to Doug Ross, Kovac was a much darker flavor of handsome cad, a Croatian immigrant haunted by the death of his family during the Balkan civil war. Visnijc is an excellent actor and Kovac was an arresting figure, particularly in early seasons, before he just got too muddled and dark. His romance with Abby Lockhart made the most sense, but the two characters were too depressed to co-exist for extended periods of time. Eventually, Kovac replaced Carter as the protagonist of the recurring "trips to Africa" subplot and underwent all kinds of horrible trauma, but the writers managed to tie up the bow nicely by the end.

12. Susan Lewis (Sherry Stringfield)

(Seasons 1-3 and 8-12, Guest Star in Season 15) Lewis had two runs on the show, one far more memorable than the other. As part of the original cast, she was the most emo of the central doctors, sleeping with a married doctor and trying to help out a drug-addicted sister. Her unresolved relationship with Greene is probably what she's best-known for, and her original departure episode "Union Station" is a great tear-jerker moment in season 3. She returned in season 8 and stuck around for quite a while, but they never knew what to do with her; Greene was married and dying, and a romance with Carter fizzled before it even began. Lewis was a much more cheerful presence later on, but eventually just got phased out to little fanfare.

13. Jerry Markovic (Abraham Benrubi, Seasons 1-15)

(Recurring in Seasons 1-5, 8-12, 15) The greatest of all the desk clerks, Jerry was in and out as Benrubi got steadier jobs on other TV shows, with no explanation given for his absences. A big, friendly cuddly bear of a man, he was another core part of the background ensemble.

14. Angela Hicks (CCH Pounder)

(Recurring in Seasons 1-4) Probably the greatest unsung doctor, and never part of the credited cast (although Pounder was nominated for an Emmy for Supporting Actress), Hicks was a wise, stabilizing force in early seasons, an especially important mentor to Benton and Carter as they climbed the surgical ranks (and abandoned ship to become emergency medicine specialists, in Carter's case). She also just got naturally phased out, with no real explanation given.

15. Neela Rasgotra (Parminder Nagra)

(Seasons 10-15) Fresh off of Bend it Like Beckham, Nagra was one of the core members of the final seasons' cast, rising to lead status by the 15th season. A shy and reserved Brit of Punjabi Sikh descent, Rasgotra was alternately steely and nervous and always incredibly likeable (can you tell that I tend to like the sterner doctors?) with two romantic pairings (to Drs. Gallant and Barnett) that were each charming in their own ways (and fraught with invented drama and severed limbs, sigh).

16. Jeanie Boulet (Gloria Reuben)

(Seasons 2-6, Recurring in Season 1, Guest Star in Season 14) Original a physical therapist who embarked on a brief affair with Benton, Jeanie joined the cast full-time as a physician's assistant and became best known for being diagnosed as HIV positive; the show explored her diagnosis with maturity basically unseen on television up to that point. Boulet was a soft-spoken and increasingly quiet presence on the show and departed rather naturally and happily, dropping in for a guest appearance in season 14 to critical applause.

17. Abby Lockhart (Maura Tierney)

(Seasons 6-14, Guest Star in Season 15) Starting out as a nurse and rising to senior ER doctor, Abby was the third longest-running character on the show and the de facto lead once Carter left. For her troubles she was saddled with the heaviest baggage of anyone on ER, from her bipolar mother (Sally Field) to struggles with alcoholism to being assaulted by her neighbor and kidnapped by gang members. Abby's drama often overwhelmed her core character, always played with as much dignity and strength as Tierney could muster.

18. Chuny Marquez (Laura Ceron)

(Recurring Seasons 1-15) For a backgrounded nurse character, Chuny got occasionally juicy material, having brief flings with Greene in season 3 and Kovac in season 9.

19. David Morgenstern (William H. Macy)

(Recurring Seasons 1-4, Guest Star Season 15) The original boss, Macy made Morgenstern a lovable, slightly absent-minded father figure for the staff, famously telling Dr. Greene he should "set the tone" in the pilot episode when Hathaway got wheeled in after her suicide attempt. He departed in season 4 after suffering a heart attack, and showed up once more in the "greatest hits" final season.

20. Lucy Knight (Kellie Martin)

(Seasons 5-6) Oh, Lucy! The sweetest little med student didn't last long on the show because Martin asked to be written out because she neither enjoyed being on a medical show nor thought the character was a real standout. I disagree, Kellie! Knight was just coming into her own (defined early on by her flirtation with Carter) before she was brutally stabbed to death by an escaped mental patient in season 6. That was the first death of a major character, and kinda the day the innocence died on ER.

21. Malik McGrath (Deezer D)

(Recurring Seasons 1-15) Malik was a big dude, and even more so than Jerry was there when some crazed tweaker had to be restrained and tied down. One of the core nurses who never stopped appearing in the show's 15 seasons.

22. Maggie Doyle (Jorja Fox)

(Recurring Seasons 3-5) ER should have paid to keep Fox around (she departed for The West Wing and then CSI). Appearing before Weaver came out, she was the show's first major gay character (although her orientation was much more obliquely referenced) and just the kind of admirable no-nonsense physician ER had plenty of in the early seasons. Later years demanded everyone have some kind of crippling personal drama, but Doyle mostly just did her job well.

23. Frank Martin (Troy Evans)

(Guest Star Season 1, Recurring Seasons 6-15) Evans played a cop who got shot in the leg in a season 1 episode and returned to become the crankier of the two big galoots behind the desk. Frank was ornery as hell and not remotely evolved in his political beliefs but pretty fun all the same.

24. Yoshi Takata (Gedde Watanabe)

(Recurring Seasons 4-10) Yoshi was the one nurse they added who really had a fair amount to do, but eventually he just stopped appearing. He's high on the list partly because Gedde Watanabe is great in Sixteen Candles and Gung Ho.

25. Michael Gallant (Sharif Atkins)

(Seasons 7-10, Recurring Seasons 11-12) A med student who joined the U.S. Army Reserve to pay for his studies, Gallant was quiet and unobtrusive, but prone to occasional outbursts (and he was usually right about stuff, especially when clashing with Pratt). The show never totally knew what to do with him, then suddenly shipped him off to Iraq and married him to Neela before killing him off, using him mostly as a prop to explore the tragic consequences of the war.

26. Ray Barnett (Shane West)

(Seasons 11-13, Guest Star Season 15) Barnett was suuuuch a ridiculous corny cliché—the rockstar med student who was more interested in his band than ER rotations—but West did his best to rise above the material and often succeeded, surprising given his background in cheesy teen drama. Barnett got done wrong by the writers (he was written off in a horrible limb-severing accident) but they eventually did him good by reuniting him with his OTP Neela in the final season.

27. Donald Anspaugh (John Aylward)

(Recurring Seasons 3-15) The jowly Anspaugh replaced William H. Macy's Morgensten as the top hospital authority figure for the rest of the show and would occasionally show up and jowl at people very proficiently. Jowl jowl jowl.

28. Sam Taggart (Linda Cardellini)

(Seasons 10-15) I love Linda Cardellini, but Sam Taggart was a mess in the Abby Lockhart mold—there just wasn't a plot she could come out of unscathed. Introduced as the chief nurse character after Abby got kicked up to doctorhood, Sam was always wrestling with personal drama or her single motherhood in fairly overwrought ways. She ends up with Tony Gates, which, shrug.

29. Conni Oligaro (Conni Marie Brazelton)

(Recurring Seasons 1-10) I've run out of things to say about the background nurses, but I sure missed Connie after she mysteriously disappeared following the tenth season.

30. Janet Coburn (Amy Aquino)

(Recurring Seasons 1-15) One of those great examples of an ER recurring character who never went away. Aquino appeared 26 times over 15 years as head obstetrician Coburn, probably most memorably in season one's "Love's Labor Lost" when she intervenes in Greene's botched delivery of a baby. At one point, she was Abby's AA sponsor.

31. Jing-Mei Chen (Ming-Na)

(Seasons 6-11, Recurring Season 1) I loved Chen when she was called "Deb" and was a rival medical student to Carter; when she came back in season six she was never given nearly enough material, doing solid work with underwhelming storylines during the show's real fallow period. I don't even remember why she leaves.

32. Lydia Wright (Ellen Crawford)

(Recurring Seasons 1-15) Lydia is the nurse who gets married early on in the show, back when the nurse characters talked more and had fun little background storylines.

33. Archie Morris (Scott Grimes)

(Seasons 10-15) Morris was a downright unemployable med student at first who did insane things like smoke confiscated pot on the job and antagonizing a mental patient who leaves the hospital, hijacks a tank, and returns to kill him. Eventually, Morris shaped up after being made Chief Resident, and I guess he got lovable, but I never fully believed in his transformation.

34. Lily Jarvik (Lily Mariye)

(Recurring Seasons 1-15) One of the less-memorable nurses, Lily was nonetheless hovering around in every season.

35. Jack Kayson (Sam Anderson)

(Recurring Seasons 1-14) Another long-running recurring character, Kayson was head of Cardiology and really mean, often coming downstairs to pick fights with the poor doctors. At one point he has a heart attack and his life is saved by Lewis; another time he leads a medical inquiry against Corday.

36. Randi Fronczak (Kristin Minter)

(Recurring Seasons 2-10) The other long-running desk clerk, and probably the sassiest. Where did Randi go after season 10? The show had stopped having fun with its classic ensemble at that point.

37. Anna Del Amico (Maria Bello)

(Season 4, Recurring in Season 3) Anna could have been a star, but she's really only a big deal in one season, where she has a long-running flirtation and eventual relationship with Carter. Bello wasn't that into the show and apparently left by mutual, amicable agreement with the writers, so we never got to see things fleshed out further. But Carter was so bummed, he grew a beard.

38. Lucien Dubenko (Leland Orser)

(Recurring Seasons 11-15) I always thought Dr. Dubenko was kinda creepy. The later-years chief of surgery nursed a crush on Abby and, especially, Neela, who was way too young for him. At one point he suggested Abby should have sex with him to make sure everything was still working after he underwent prostate surgery. But he was just a harmless weirdo, really.

39. Catherine Banfield (Angela Bassett)

(Season 15) Banfield was a late addition in the last season with a complicated backstory that allowed the show to bring back Mark Greene for a flashback episode. Aside from that, she wasn't that interesting but benefitted from being played by Angela Bassett, who rocks.

40. Tony Gates (John Stamos)

(Seasons 13-15, Recurring Season 12) The final, and weakest, attempt the show ever made to introduce a Really Handsome Dude. Gates is basically the male lead in the final, forgettable seasons, which are only worth remembering for all the episodes where they brought back beloved former stars. He dated Neela for a while, then Sam, and in neither case was it interesting.

41. Cleo Finch (Michael Michele)

(Seasons 6-8) One of two disastrous additions to the cast after George Clooney departed, Cleo Finch was a pediatric fellow who was sadly never interesting. Not remotely, not once. She wasn't annoying either; there's really nothing to say about Finch except that she leaves the show with Benton, who she ends up with. Good for her!

42. Kevin Moretti (Stanley Tucci)

(Seasons 13-14) A ridiculous antagonist boss thrown into the mix once ER casting was simply based on casting around for famous people. He had a one-night stand with Abby, temporarily breaking up her relationship with Luka, and eventually gets punched in the face for it, his most memorable moment.

43. Victor Clemente (John Leguizamo)

(Season 12) An even more ridiculous antagonist boss who wanted desperately to be in charge and clashed with every character he met. Eventually he went insane and got fired. One of the most regrettable story arcs in ER's history.

44. Simon Brenner (David Lyons)

(Seasons 14-15) This "charming" douchebag, a nephew of Anspaugh's, liked to sleep with med students and not do work. Lyons went on to play the titular hero of The Cape, and I wish that had been his character on ER too.

45. Dave Malucci (Erik Palladino)

(Seasons 6-8) A hot-headed, insubordinate bag of rebellious clichés that got barfed onto the hospital in season six and marked an immediate downturn in quality. He was always an idiot and was justifiably fired by Weaver in season 8 for accidentally killing a patient due to negligence and having sex in an ambulance. As he left the hospital he called Weaver a "Nazi dyke." He was born to be at the bottom of this list.

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