Continuity mistake: As Mark futilely pounds on Jodi O'Brien's chest, Carol can be seen in the background, removing her protective glasses with one hand. However, after the Time of Death has been called and they're showing the reactions of everyone present in the room (Susan, Carol, Carter, Lydia, Chen), Carol is seen taking the glasses off again, this time with both hands.
Visible crew/equipment: When the son of the accident victims is being led through the trauma rooms to see his parents' bodies, you can see Laura Innes crouching under a table in the background directing the scene. Innes was the director of this episode and it was established that this episode took place on her character's day off. Therefore, she should not have appeared in front of the camera at all.
Plot hole: There are always family members right in the room while the doctors are literally cutting into the patients. The family is always creating a fuss or whatever, until someone asks for them to escorted out. A real hospital would never let family members into the room while they are cracking open their loved one's chest.
Continuity mistake: Peter goes into the operating room, demanding to help with his mother's surgery. When he goes in, his cap is pulled down over his hair, but when he is talking to the surgeon in charge, about an inch of his hair shows for a couple of shots. The surgeon orders him out, and he leaves, and his hair is completely covered again. At no time did he adjust the cap.
Continuity mistake: When Morris is on the bed following his shock there are three point of view (POV) shots. Morris on the bed, Morris's POV of the medical staff hovering over him and a shot from behind the staff looking down on Morris. The placement of characters is misaligned between views, most notably when the shot is from behind the staff looking down: there is a sizable gap between the two on the left and right, where as from Morris's POV they are clustered close together with no gaps between the staff members.
Continuity mistake: As Doug Ross sits with the little girl Kaneisha who is sleeping, her bedcovers change position noticeably in one shot, and then back to the way they were in the next. In the same shots, Doug's ID also changes from being completely noticeable to almost completely obscured, and then back again.
Continuity mistake: Doug and Peter are running to meet the ambulance transporting the boy with the crushed leg. From the back we see Doug with his arms out as he runs, but the shot changes to the front and he has his hands in his pockets, with no time to change naturally. (00:10:40)
Other mistake: Season 12, Episode "Blame it on the Rain": At the beginning of the episode, Abby is almost run over by a man driving an SUV. They exchange words and then Abby throws a supposedly full cup of coffee at him. The cup of coffee bounces off the seat of the man's car and it is obvious that the cup is empty.
Continuity mistake: Luka is in talking to the first possible kidney transplant patient - he puts his pen into his pocket and is holding the chart in his other hand, also up by his chest. As he says "Minneapolis", the shot changes and we see him put his pen in his pocket again and his chart is down by his waist - there was no time for the shift.
Continuity mistake: Carol and Carter are in the room with the patient Tatiana and the dog; Tatiana has a yellow marker in her hand. In some shots she appears to be hugging the dog and in others drawing something with the marker, with no time to change positions. (00:21:50)
Visible crew/equipment: In the last scene there are three doctors standing in the corridor (I think it's Ross, Carter and Benton). You can see their tape marks for where they need to stand. When the camera pans out it pans too far and you can see where the corridor floor ends and the studio floor starts.
Factual error: Episode Title: The Show Must Go On Season Number: 11 Episode Number 245 (22 of that season) When the woman is giving birth, they show the baby just after they finally got her out. The baby is clean, no blood and other signs of a recent birth are visible. This is especially unlikely since the doctors had to "cut her open" to liberate the baby from the birth channel.
Plot hole: During Season 5, the search for an ER Chief takes nearly a year and two nationwide searches, but is ultimately unsuccessful. At the beginning of Season 6, Romano is chosen as Chief of *Staff* in the blink of an eye, and Kerry is appointed as ER Chief just as quickly. Then, in Season 9, Kerry and Romano's positions are switched as though such things happen everyday. There's no way decisions of this magnitude would be made in such a brief amount of time.