History YMMV / ER

** In the {{Pilot}}, Susan diagnoses a patient named Mr. Parker--played by Creator/MiguelFerrer (Creator/GeorgeClooney's cousin)--with cancer. Ferrer later died from throat cancer in 2017.

* OnceOriginalNowOverdone: When the show started airing, it was absolutely ground-breaking for a medical drama, and in the process, it was also completely divorcing itself from the soap opera genre, where all the other medical dramas made before ''ER'' firmly belonged. To say nothing about having a highly realistic portrayal (at least for its era) of medical procedures. Fast forward a few decades, and everything that made the show stand out became commonplace, making it hard to appreciate without the right context just how revolutionary it was back in the early 90s.

* OnceOriginalNowOverdone: When the show started airing, it was absolutely ground-breaking for a medical drama, and in the process, it was also completely divorcing itself from the soap opera genre, where all the other medical dramas made up until ''ER'' firmly belonged. To say nothing about having a highly realistic portrayal (at least for its era) of medical procedures. Fast forward a few decades, and everything that made the show stand out became commonplace, making it hard to appreciate without the right context just how revolutionary it was back in the early 90s.

* OnceOriginalNowOverdone: When the show started airing, it was absolutely ground-breaking for a medical drama, and in the process, it was also completely divorcing itself from the soap opera genre, where all the other medical dramas firmly belonged. To say nothing about having a highly realistic portrayal (at least for its era) of medical procedures. Fast forward a few decades, and everything that made the show stand out became commonplace, making it hard to appreciate without the right context just how revolutionary it was back in the early 90s.

* SeinfeldIsUnfunny: When the show started airing, it was absolutely ground-breaking for a medical drama, and in the process, it was also completely divorcing itself from the soap opera genre, where all the other medical dramas firmly belonged. To say nothing about having a highly realistic portrayal (at least for its era) of medical procedures. Fast forward a few decades, and everything that made the show stand out became commonplace, making it hard to appreciate without the right context just how revolutionary it was back in the early 90s.

** [[{{Yandere}} Steve Curtis]] is the ex-boyfriend of Nurse Samantha Taggart, and the father of her son, Alex. [[DisappearedDad An unreliable deadbeat]], Steve nevertheless becomes obsessed with re-inserting himself into Sam and Alex's lives, and after being arrested for armed robbery, he concocts an escape plan with another prisoner named Rafe Hendricks, and an EMT named Mary. Steve and Rafe fake a fight that gets them brought to Cook County, where they grab Sam after being freed by Mary. When the getaway goes awry, Steve and Rafe shoot up the hospital, injuring and possibly killing numerous people, before taking off with Sam and a kidnapped Alex. [[RunForTheBorder On the way to Canada]], Steve [[YouHaveOutlivedYourUsefulness guns down Rafe and Mary]]. Afterward, Steve implies that he is willing [[PaterFamilicide to kill Sam, Alex, and himself]] rather than see them all be separated again, right before he rapes Sam.

** Conversely the cops complain that he didn't do a good enough job, noting that he shot the guy five times and he still survived, and claiming that if the police had caught up with him, he'd be in the morgue instead. Which kind of takes things into KickTheSonOfABitch territory, given how hard it is to hit a moving target at distance even when you've not just been shot, and it's hardly the guy's fault that the psycho was [[MadeOfIron too tough to die after being hit by five bullets]].

* Protagonist-Centered Morality: Abby is seemingly terrible at the scientific aspects of medicine, being unable to answer basic questions about biochemistry posed by Dubenko to her cohort of interns and failing her board exam. She all but says that "real doctors" act on instinct and empathy and don't waste time with biology and chemistry. At the same time, the show perspective takes it for granted that Abby is entitled to her dream relationship despite never permanently getting her alcoholism under control and cheating on her husband while he was away attending to his dying father. Abby and Luka quickly reconcile and are given a "happily ever after" sendoff in their final appearance on the show, without any real resolution to these years-long storylines about the former protagonist of the series before she departs and is never mentioned again.

* ActorShipping: Creator/GeorgeClooney and Creator/JuliannaMargulies, aka SuperCouple Doug and Carol. The two burst out laughing when asked if they were dating in RealLife, but years after the show ended, admitted that they'd been attracted to each other throughout their time on the show and that to this day (they've remained good friends), they use their characters names as pet names for each other.

** Something is definitely ''off'' about Chloe Lewis, given her massive self-indulgent ego and inability to feel sympathy for anyone around her. There is an attempt to diagnose her in season 1, but nothing much comes of it.

** Something is definitely ''off'' about Chloe Lewis, given her massive self-indulgent ego and inability to feel sympathy for anyone around her. There is an attempt to diagnose her in season 1, but nothing much comes of it. ** Luka Kovač has bouts of what appears to be clinical depression several times throughout his time on the show, but it's never officially diagnosed and the only time he appears to be seeking help, it turns out he's confiding in a prostitute. He also appears to suffer from PTSD as well.

* AcceptableHardLuckTargets: Psychiatric patients were uneven targets of DependingOnTheWriter. There were many mentally ill patients who were written seriously, but plenty ''more'' whose behavior was played for laughs, or were portrayed as terrifying, nearly inhuman forces of nature.
* AcceptableHobbyTargets: Adult gamers. Kovac buying himself a UsefulNotes/PlayStation to relax with (after he's been working twelve-hour shifts at one of the most stressful jobs imaginable, as the show is keen to remind us) is presented as a sign of his deteriorating mental health and that he's becoming a {{Jerkass}}. Bonus points for PacManFever noises as he plays. Note that this was in complete contrast with earlier seasons. Carter bonds with a leukemia patient over ''Franchise/MortalKombat'', Greene plays ''VideoGame/KillerInstinct'' at an arcade to take his mind off of the events of 'Love's Labour Lost'. The ER staff are all playing ''VideoGame/DoomII'' when Doug is out saving a drowning boy.

** [[{{Yandere}} Steve Curtis]], introduced in Season 10's "Where There's Smoke", is the ex-boyfriend of Nurse Samantha Taggart, and the father of her son, Alex. [[DisappearedDad An unreliable deadbeat]], Steve nevertheless becomes obsessed with re-inserting himself into Sam and Alex's lives, and after being arrested for armed robbery, he concocts an escape plan with another prisoner named Rafe Hendricks, and an EMT named Mary. Steve and Rafe fake a fight that gets them brought to Cook County, where they grab Sam after being freed by Mary. When the getaway goes awry, Steve and Rafe shoot up the hospital, injuring and possibly killing numerous people, before taking off with Sam and a kidnapped Alex. [[RunForTheBorder On the way to Canada]], Steve [[YouHaveOutlivedYourUsefulness guns down Rafe and Mary]]. Afterward, Steve implies that he is willing [[PaterFamilicide to kill Sam, Alex, and himself]] rather than see them all be separated again, right before he rapes Sam.
** Season 6: [[SerialRapist Dean Rollins]] initially appears to just be a run-of-the-mill accident victim, but is soon discovered to be a vicious SerialKiller. While being treated for life-threatening injuries, Dean is forced by Doctor Lizzie Corday to reveal the whereabouts of his latest victim, Sandra. Sandra, who was raped and stabbed, dies while being treated at Cook County, with Dean proceeding to mock Lizzie over how his confession being coerced means that it had to be thrown out by the DA. He goes on to demean Lizzie by getting her to say that she cares about him "as a woman" in exchange for agreeing to undergo a lifesaving surgery, and later has her bring him Lindsey, the sister of a victim named Jenny, by falsely promising to reveal the whereabouts of Jenny's remains to Lindsey. He feigns sympathy for Lindsey, and then taunts her by saying, "If only I'd met you... I could've had you instead!" Eventually growing weary of being bedridden and largely powerless as he awaits his trial, Dean tries one final time to exercise control over Lizzie by attempting to [[BetterToDieThanBeKilled coerce her into breaking her Hippocratic Oath by euthanizing him]] in exchange for information about Jenny.
** "Carter's Choice": [[TeensAreMonsters Jack Miller]] is a young SerialRapist who preys on [[WouldHarmASenior elderly women]], who he [[NoHoldsBarredBeatdown brutally beats]] before sexually assaulting them, afterward using a marker to brand the victims with the word "WHORE". Jack's first known victim is 67-year-old Mrs. Larkin, with the second being a dementia sufferer named Ann. The third victim dies from her injuries, while the fourth one--[[AScarToRemember who had "WHORE" carved directly into her flesh]]--nearly dies from wounds sustained from being strangled and thrown down a flight of stairs while trying to fight off Jack. Jack guns down a security guard who had interrupted his attack on the fourth victim, and is finally arrested after being shot during a standoff with the Chicago PD.
** "Where the Heart Is" & "Rampage": [[AbusiveParents Derek Fossen]] is a temperamental man who once [[DomesticAbuse beat his girlfriend]], and is now abusing his young son, Ben. After Ben is taken by social services at the behest of Doctor Mark Greene, Derek snaps and [[SpreeKiller goes on a shooting rampage]] through Chicago in search of his son, while also attacking everyone who he [[NeverMyFault blames]] for him losing custody of Ben. Derek shoots up a foster care facility [[WouldHurtAChild full of children]], guns a man down for his car, and opens fire on his neighbor and her son before running over a member of the Chicago PD. Derek makes a failed bid to murder Mark's family and shoots five more people before being wounded by a bystander and taken to Cook County, where he is allowed to die from his injuries by an enraged Mark.

** Throughout the first few seasons of the show, many of its guest stars would go on to fame of their own--Creator/LucyLiu, for example, spent several episodes playing the mother of an AIDS-stricken infant, Creator/BradleyWhitford played the grieving husband of a woman who died in childbirth, Creator/KirstenDunst played a runaway, etc.

** Season 6: [[SerialRapist Dean Rollins]] initially appears to just be a run-of-the-mill accident victim, but is soon discovered to be a vicious SerialKiller. While being treated for life-threatening injuries, Dean is forced by Doctor Lizzie Corday to reveal the whereabouts of his latest victim, Sandra. Sandra, who was raped and stabbed, dies while being treated at Cook County, with Dean proceeding to mock Lizzie over how his confession being coerced means that it had to be thrown out by the DA. He goes on to demean Lizzie by getting her to say that she cares about him "as a woman" in exchange for agreeing to undergo a lifesaving surgery, and later has her bring him Lindsey, the sister of a victim named Jenny, by falsely promising to reveal the whereabouts of Jenny's remains to Lindsey. He feigns sympathy for Lindsey, and then taunts her by saying, "If only I'd met you... I could've had you instead!" Eventually growing weary of being bedridden and largely powerless as he awaits his trial, Dean tries one final time to exercise control over Lizzie by attempting to [[BetterToDieThanBeKilled coerce her into breaking her Hippocratic Oath by euthanizing him]] in exchange for information about Jenny.
** "Where the Heart Is" and "Rampage": [[AbusiveParents Derek Fossen]] is a temperamental man who once [[DomesticAbuse beat his girlfriend]], and is now abusing his young son, Ben. After Ben is taken by social services at the behest of Doctor Mark Greene, Derek snaps and [[SpreeKiller goes on a shooting rampage]] through Chicago in search of his son, while also attacking everyone who he [[NeverMyFault blames]] for him losing custody of Ben. Derek shoots up a foster care facility [[WouldHurtAChild full of children]], guns a man down for his car, and opens fire on his neighbor and her son before running over a member of the Chicago PD. Derek makes a failed bid to murder Mark's family and shoots five more people before being wounded by a bystander and taken to Cook County, where he is allowed to die from his injuries by an enraged Mark.
** [[{{Yandere}} Steve Curtis]], introduced in season 10's "Where There's Smoke", is the ex-boyfriend of Nurse Samantha Taggart, and the father of her son, Alex. [[DisappearedDad An unreliable deadbeat]], Steve nevertheless becomes obsessed with re-inserting himself into Sam and Alex's lives, and after being arrested for armed robbery, he concocts an escape plan with another prisoner named Rafe Hendricks, and an EMT named Mary. Steve and Rafe fake a fight that gets them brought to Cook County, where they grab Sam after being freed by Mary. When the getaway goes awry, Steve and Rafe shoot up the hospital, injuring and possibly killing numerous people, before taking off with Sam and a kidnapped Alex. [[RunForTheBorder On the way to Canada]], Steve [[YouHaveOutlivedYourUsefulness guns down Rafe and Mary]]. Afterward, Steve implies that he is [[PaterFamilicide willing to kill Sam, Alex, and himself]] rather than see them all be separated again, right before he rapes Sam.

* TheyChangedItNowItSucks: Seasons 13-15 having [[ReplacedTheThemeTune the theme tune replaced]] with a shorter intro produced by series music composer Martin Davich did not bide well with the fanbase viewers who have been so accustomed to full-length opening credits and hearing James Newton Howard's initial/original theme music for 12 seasons.

* TheyChangedItNowItSucks: Seasons 13-15 having [[ReplacedTheThemeTune the theme tune replaced]] with a shorter intro produced by series music composer Martin Davich did not bide well with the fanbase viewers who have been so accustomed full-length opening credits and hearing James Newton Howard's initial/original theme music for 12 seasons.

* TheyChangedItNowItSucks: Seasons 13-15 having [[ReplacedTheThemeTune the theme tune replaced]] with a shorter intro produced by series music composer Martin Davich did not bide well with the fanbase viewers who have been so accustomed to hearing James Newton Howard's initial/original theme music for 12 seasons.