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.
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.
Deliberate mistake: The show regularly shows characters by the Chicago River and either on or near Michigan Avenue, when they are getting lunch or walking to work. Both U of C hospital (where the hospital exteriors are filmed) and Cook Country hospital (where the characters are supposed to work) are about 5 miles from this point. This would be an extremely long distance for them to walk on a routine basis. I'm sure this is done just because Michigan Ave and the river are two of the most scenic parts of Chicago.
Factual error: Featured characters in the show always seem to be wearing brand new winter clothing - their jackets, hats, gloves, etc. always look pristine, sparkling clean, and just-purchased. Anyone who lives in a winter climate knows that winter clothes age very quickly - the pristine look last about an hour. Extras in the show, probably providing their own clothes, wear much more lived-in normal outdoor clothing.
Continuity mistake: In season one (Thanksgiving episode) and in Season 2 (his graduation) Carter says he has a sister. After these seasons when his family is very involved in multiple plotlines there is no sister.
24 Hours (1) (a.k.a. The Longest Day (1)) - S1-E1
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.
24 Hours (2) (a.k.a. The Longest Day (2)) - S1-E2
Visible crew/equipment: When Dr. Greene goes into the lab with Mrs. Raskin, the boom mic is reflected in the glass behind them.
Chicago Heat - S1-E7
Visible crew/equipment: After Dr. Benton talks to the police detective and then goes to see the grocery store owner, as Dr. Benton swings open the doors, the camera crew can be seen in the reflection of the glass of the door.
Chicago Heat - S1-E7
Continuity mistake: Near the start of the show, Carol is on the phone in the ER - we can see her name tag pinned over the right side of her stethoscope. In the next shot, as she turns to talk to Mark, the tag is pinned over the left side of the stethoscope.
Chicago Heat - S1-E7
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: When Susan and Chloe are fighting in front of the desk, you can see 2 marks on Susan's right shoulder that look like blood with no obvious source from previous scenes. While Chloe is having her hand treated, Susan is standing outside the door and turns, and the marks have disappeared. (00:35:05 - 00:35:50)
Continuity mistake: Carol is seen walking into the ER twice at the beginning of the episode.
Continuity mistake: Haleh puts a bow on the top of the organ cooler, the next shot it is on the side.
Continuity mistake: Benton's stethoscope moves between shots as he talks to Hicks about failing to get allowances to harvest a patients organs for donation. As he comes out of the room the stethoscope lies over his shoulders, in the next shot of Benton it's hanging round his neck.
Long Day's Journey (a.k.a. Missing Persons) - S1-E15
Continuity mistake: Doug Ross puts a piece of gauze over the young girl Mandy's wrist - the shot changes to over his shoulder and there is suddenly no gauze. Within a few seconds he then manages to bandage up her hand, as he talks. In real time, it couldn't have been done that quickly.
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)
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)
Continuity mistake: Carol goes to visit Tatiana while she is sleeping. As the camera shows a shot from above, the blanket over the girl has changed position noticeably. (00:31:40)
Continuity mistake: At the very end of the show, Carol is sitting on a gurney with Tatiana - the little girl is holding her doll by its waist. The shot changes and suddenly she is holding it around its neck.
Visible crew/equipment: When Dr. Greene says "It's my daughter's birthday too" a boom mic is visible.
Answer: Take care of your dad.