Kerry and Jeanie's relationship. Everybody hates Kerry and she's patronising, annoying and potentially hostile to practically all her co-workers. But Jeanie seems to bring out her kinder, gentler side, and Kerry, without hesitation, agrees to monitor her health in case her condition deteriorates.
Ditto Kerry's relationship with Abby Lockhart — Kerry genuinely cares for her, and Abby seems to see (and bring out the best in) Kerry.
Pretty much any time Romano is nice (and genuinely nice) to someone else, not for the sake of reputation or a reward. Usually, whenever Romano and Corday have a sweet moment together.
In one early episode, a woman comes to Dr. Lewis with abdominal pain. Susan performs an ultrasound, revealing that the patient is going to have a baby. "A baby?" the patient says in consternation, and then a moment later, sounding absolutely delighted: "My baby?" She and her husband had tried for years to have a child, without any success; she's so elated to hear the news she grabs Susan in a bear hug.
Almost the entirety — but especially the first ten minutes or so — of "Blizzard". Susan and Mark put a cast on Carter's leg ("Because sticking his hand in a bucket of warm water would be juvenile"); the nurses and Jerry play their own version of office soccer, using biohazard bins; Mark, Susan, and some other staff have a snowball fight in the ambulance bay; we find out that Carol is now engaged to Tag, and moments later Doug enters the ER and congratulates her.
A thoroughly exhausted Doug being led out of the hospital by Mark at the conclusion of "Hell And High Water" Unfortunately, as soon as they walk out, they are absolutely swarmed by reporters wanting to question him about his heroic actions. Poor Doug's reaction is almost fearful—he ducks away from the cameras and lights and tries to turn his back. Seeing this, Mark reacts in a very protective, big brother like manner, trying to shield him and keep the throng at bay. It's already a touching moment, even more so if you recall that they've been at each other's throats for several episodes prior to this.
Loretta, a single mother, former prostitute and ER regular, asking if Mark would be godfather to her two kids when she's dying of cervical cancer. Something of a Tear Jerker as neither Loretta nor her kids are seen or mentioned again after that episode.
Jeanie anticipated being shunned and avoided by her coworkers after revealing her HIV status to them; instead she has their continued respect, support and friendship. Her husband Al, having just broken up with her, drops by the ER shortly before Christmas with some of her things, including a tree topper that they'd bought for their first Christmas together. Jeanie puts it on the tree in the ER, prompting Randy to comment, "You should put it on your family tree." Jeanie's response? "I just did."
The beginnings of Mark and Elizabeth's relationship is pretty heartwarming. Including their first real interaction in Season 4 when Mark says "You've been here for six months. You can call me Mark."
Jeanie's friendship with Scott Anspaugh.
One for DR and CAPT Greene is when Mark takes his dad to the base hospital, and a major, multiple patient, trauma event comes in. The ER is short staffed, Mark volunteers, and scrubs in to help. Hours later, an exhausted Mark sees, maybe for the first real time, the pride in his dad's face.
In "Something New", Doug asks Carol if he can have a drawer at her place to keep a change of clothes in, since they've rekindled their relationship and he's staying over at Carol's every night. Carol is initially unsure, but at episode's end she makes Doug wait on the porch while she brings him a present, something huge wrapped in gift paper. It's a drawer from her dresser.
A few weeks later, as he prepares to leave town to make arrangements for his father's funeral, Carol tells him she's going to miss him. He smiles and tells her he loves her. After he drives off, she says the same thing. It's a very touching moment with a Meaningful Echo—the only time we'd heard him say this before was in a desperate bid to keep her from marrying another man. Now, he's gotten his life together and can say it from a place of peace.
In that same episode, there was Romano's reaction after Lucyis pronounced dead. He stares for a moment, then starts charging the paddles again, saying, "No, let's go again."
Then at the end of the episode, Weaver and Romano work together on cleaning Lucy up.
Mark's father and Elizabeth's mother having a good-natured "my kid is more awesome than yours" conversation.
As well as Mark and Elizabeth's visibly shocked reaction to this, as they'd both spent years clashing with their respective parents because they felt their parents acted as though they were disappointed with them—only to have it turn out they were actually quite proud.
Greene taking his dying father for a last boat trip, after hearing him talk about how peaceful he found it after returning from Vietnam.
Several months after the stabbing, Carter develops an addiction to painkillers, and in the Season 6 finale, Mark, Benton, Kerry, Jing-Mei, and Anspaugh try to get him to go to a rehab center in Atlanta. Words are had, Carter quits and angrily punches Benton...then dissolves into tears, horrified and ashamed. Benton hugs him, in that faintly irritated Benton way he has, and the next time we see them, they're side-by-side on the plane to Georgia.
Benton: You wanna Fight, we'll fight. But one way or another, you're getting your ass in that van.
Romano sending Elizabeth ice-cream and pizza—she mentioned she was craving them—after a long operation when she is seven months pregnant. The food comes with a note: "Great job Mom!"
Romano's concern when Elizabeth is threatened by the madman rampaging around Chicago, and his relief when it turns out she's okay.
"Sailing Away". Abby's mentally disturbed mother has been missing for months and finally turns up in Oklahoma. Abby is desperate to find her and take care of her, but can't find an available flight out. Carter not only pulls some strings to get her her flight, but books one for himself to accompany her and helps Abby take care of her mother throughout the entire episode by driving, buying breakfast, you name it. After they get home in Chicago near the end of the episode (before shit hits the fan), the typically-stoic Abby sincerely thanks Carter for everything he's done to help.
In an early Season 7 episode, Abby (as a nurse) has assisted with the delivery of a micro-premature baby. She spends the entirety of the episode with the father and mother of said baby, ensuring that they get the absolute care and compassion that they very much deserve. This extends to her demanding Randi call priests when the chaplain is unavailable, putting a doctor in his place after he "shows off" said micro-preemie to a group of med students without the parents consent or awareness and watching the baptism.
When Benton leaves for good in Season 8, Carter catches up to him during one of his runs and gives him a gift: an L token, which Benton gave to him during his internship as a challenge during a very difficult shift.
Carter: I'm a good doctor because of you. Benton(smiling) No, you're not. But keep trying.
A whopping seven seasons later, in Season 15's "Old Times," Benton can be seen wearing the L Train token as a necklace, which he's taken to wearing in his new role at the medical center. Benton never calls attention to it, but the fact that he still has it all this time later makes it much more meaningful to his friendship with Carter.
In the episode "Bygones", Ella's babysitter brings her to the ER and both Mark and Elizabeth are worried, Ella had overdosed on amphetamines several weeks ago. As it turns out it was nothing serious, Ella was just saying her first words and the babysitter wanted her parents to hear them. Her first word? "Dada."
There was a small moment in one episode when Romano was being all hard-nosed towards Benton when Benton was complaining about how much he was struggling to care for his son Reese (who was deaf); Benton turns and stalks off angrily, carrying Reese as he goes. But as he leaves, and Reese is staring at Romano over Benton's shoulder, Romano signs "take care of your daddy" to Reese. Reese even seems to nod back.
After Weaver came out to Romano in the heat of the moment, she takes a vacation and then returns to work terrified that he's told everyone. But when she asks him, he's genuinely shocked that she thought he would do it; it's confidential information, and completely up to her who knows.
Despite appearing to be in love with Elizabeth, Romano gently comforts and supports her when she's devastated over Mark's cancer returning. He is also the one who helps her decide to go back to Mark at that point.
Romano: Is he your husband? Do you love him? Then that's your answer.
"Orion in the Sky" features Mark's last day in the ER and the last patient he treats is a little girl with a splinter under her nail. She describes the titular Orion to him, while he pulls the splinter out without her even noticing. Mark then thanks her because she become his last patient.
Girl's Father: End of shift? Mark:(smiling) Yes.
As Mark is dying in "On the Beach", we see into his head and him in his scrubs, walking through a clean, empty ER. Everything has been dealt with. All patients have been seen and taken care of. Mark has no more 'work' left to do and is... done. A painful Tearjerker as well, but it shows that he is dying contently.
In "The Letter", a letter from Dr. Greene is faxed to the ER, and Carter reads it for everyone. The last page is an afterword by Dr. Corday, stating that Mark had died that morning, and that she wanted them to know his feelings for them before his death. Carter has the letter posted on the board for all to read.
Carter: Post that on the floor, Frank. Frank: That last part? Carter: The whole thing.
Rachel with regards to Ella. Even the episode where Ella accidentally overdoses on Rachel's ecstasy has some endearing moments between the two, such as at the start of the episode when Rachel happily offers to watch her little sister and is shown playing very cutely with her. Despite her previous behavior of lying to her father and step-mother she immediately confesses to having had drugs in the house when she realizes Ella might have taken it (which must have taken a lot of guts) and shows a lot of concern for her sister during the rest of the episode. Later on, after Mark's funeral, she asks Elizabeth if she can come visit Ella to which Elizabeth responds: "Of course. She's your sister".
Another one where Romano just had surgery to remove his bad arm, Doctor Corday (who is arguably his only friend) is sitting next to him and assuring him it went well. Still a little bit dazed, he tells her in an absolutely child-like voice that he loves her.
In the episode "The Lost", after believing that Kovac was killed in Africa, Carter travelled all the way from Chicago to find his body and bring him home, despite the dangers that laid ahead. That alone was an act worthy of a Heartwarming Moment. But the real moment comes in a flashback, where Kovac was about to be shot by the soldiers, he began praying to God, whom he said that he said he didn't believe in anymore. And, while he was praying, the soldiers saw the necklace he was wearing of the cross and were led to believe that he was a priest and they wouldn't dare harm a "man of God". Even though the soldiers quickly dropped to their knees in prayer with him, Kovac continued praying.
And later, after Carter reached Kovac and were riding back to get him back to America, a woman whose daughter Kovac had treated (and also the one who gave Kovac the necklace with the cross) reaches out to Carter and tearfully thanks him.
Corday and Romano's friendship is proven to the very end, when Corday is the only one who attended Romano's funeral.
When Carter discovers that his son was stillborn, he goes out of the room for a minute, looking positively devastated. Then, his father arrives (it's implied that Carter specifically called his dad first to tell him the news) and he runs to his father, crying and hugging him, almost like a child desperate for reassurance. And his father gently hugs him back, telling him it's going to be all right.
When an elderly patient laments how he is nearing the end of his life and how he's accomplished nothing, Abby goes out of her way to call up some of his former students to give him a visit, despite the patient being grouchy and irritable with her earlier. The surprise and joy on his face was he sees some of his students was definitely a Heartwarming Moment.
And near the end of the same episode, the patient respectfully asked if Abby could be his nurse again for tomorrow. Abby gently told him she couldn't. But she will be there at the hospital. She told him to just ask for Doctor Lockhart if he needed her. That was Abby's last shift as a nurse; she had just completed her Boards to become a doctor.
The birth of Kerry and Sandy's son, Henry. They're so happy....
At the end of "Twas the Night", a homeless lady was singing "O Holy Night", where another lady, who had been very adamant against Christmas and everything to do with it throughout the whole episode (even taking away Christmas ornaments from the counter), sees her singing, looks at her and walks away with a defeated look on her face.
From the same episode, a little girl, whose brother had gotten in a car accident, mentioned that Santa won't come for her because she had thrown a book out of the window, which made her brother go out of the car to get it, causing the other car to hit him. Later on, a young boy asked Abby and Neela if there was a chimney in the hospital, so Santa could get him a present. However, the boy's father was too poor to even afford one. So Abby and Neela went around delivering presents secretly to both the little girl and the little boy. The boy's father's expression as Abby sets a new truck toy for his sleeping son was more than enough to express his gratitude.
At the end of "Refusal of Care", there was just something so heartwarming to hear Dr. Lewis sing a little song for her sick son Cosmos over the phone. Not to mention, while she was singing, we see that a woman, who was starving herself to save her son, finally takes a bite to eat, and another woman, who was against getting treatment for cancer, being wheeled to go get it, after talking with a survivor of cancer, who is seen holding her hand.
In "Nobody's Baby", after giving birth to a brain damaged boy, the surrogate mother didn't want him and neither do the boy's actual parents. So Ray decides to spend the night with the baby, just so he doesn't have to be alone.
At the end of "Two Ships", after all the chaos that had happened, a tired Neela comes home for a rest, only to turn around and see that Michael had finally returned from the army. The joy on Neela's face as she runs towards him for a hug is indescribable.
In "All About Christmas Eve", a little six-year-old is without a pulse and is dying. So, her tearful mother tells her that it was going to be all right, that her mother and father love her very much and that God is waiting for her. But then, her pulse suddenly returned to the amazement and joy of the doctors and the mother, and she is seen recovering steadily in the end. And later, the mother implied that she doesn't blame the teenagers that hurt her daughter, but rather, she hoped that they will be able to change their ways.
Also, outside the hospital, dozens of strangers are standing vigil, each holding a candle, praying for that little girl that they don't even know.
In "Strange Bedfellows", a deaf man leaned his head against the heart of his friend, who was in the hospital after a drug overdose. She explained to the confused doctors that he loved to "hear" her heart, to make sure that she was all right. After all this time, he was the only one who has ever tried to listen to her, she commented with a grateful smile to the man.
At the end of "City of Mercy", Morris spontaneously decides not to take advantage of a willing woman's interest in him. Right afterwards, walking outside in the snow, he berates himself out loud for letting her slip through his fingers, mocking his buying into the spirit of Christmas. He finishes the rant by screaming "There's no freaking Santa!!" to the city at large. Just then, a man passes by, wishing him a Merry Christmas. Morris turns and freezes, astounded, eyes fixed upon the night sky behind the camera as sleigh bells begin to jingle...
From the same episode, Sam helped a homeless woman reunite with her parents, while Neela helped an estranged father get some Christmas presents for his two kids. Meanwhile, Dr. Dubenko is having Christmas dinner with his sister, who is mentally seventeen, and treating her very lovingly.
Pretty the whole episode of "I Don't", when Abby and Luka finally get married. Their choosing of their maid of honor and best man (Neela and Pratt respectably), their vows, Abby (having threatened Hope earlier for being involved with her wedding) thanking her for doing this, seeing Morris and Hope getting together and many others all left many fans feel happy for them.
In "The War Comes Home", Dubenko mentioned that he had to write a lot of post-op notes to write, as he wheeled the sleeping Neela who just came out of surgery. When they settle Neela in the room, the nurse said that she will be waiting for the notes. Only for Dubenko to hand her the completed notes and sat next to Neela, holding her hand.
Throughout the episode, the rest of the ER, even the nurses, were all worried and trying to get as many updates as they could about Neela. In the end, after all the chaos was over with, they all came up to the waiting room and patiently waited for any news about Neela.
In the Season 11 finale, Carter instructs Morris to set the tone (as Greene told him to do in Season 8), only to jokingly retract his advice after seeing how hungover Morris is. As the series continued, Morris gradually got better, but following his best friend Pratt's death, he really undergoes immense Character Development, becoming one of the ER's best doctors. In "The Beginning of the End", he and Carter reunite, and Carter is quick to notice his successor's growth:
Archie's smile makes the moment all the better, as it implies that he managed to remember that conversation, or at least understood its significance.
One of the last recurring characters is an elderly man played by Ernest Borgnine dealing with the impending death of his terminally-ill wife. It's very clear he loved her for nearly 70 years, including over 60 years of marriage. In the series finale, when she finally dies, their daughter arrives. Apparently she was somewhat estranged from her mother, but in those moments, being reminded how in love her father was with her, she said she had forgotten why there was friction between them.
After hearing that, Sam called her mother.
Pretty much everything in the series finale, especially anything with Carter and Benton, and the HIV+ patient's interaction with Dr. Julia Wise, played by Alexis Bledel.
When Carter names the "Joshua Carter Centre" after his deceased infant son.
Carter taking Rachel Greene under his wing as she comes to Chicago to apply for medical school. He then invites her to tag along in a mass-casualty trauma, encouraging her to join him with a burn patient.
Carter: Dr. Greene... you coming?
In season eight a teenaged Rachel Greene has ecstacy pills in her backpack and her baby sister Ella, nine months old at the time, swallows a couple of pills, OD's, and nearly dies. After this, Elizabeth Corday (Ella's mother and Rachel's stepmother) is so furious with Rachel that she can barely stand to be near her, and Mark's refusal to send Rachel away almost ruins his and Elizabeth's marriage. After Mark's death some months later, Rachel asks Elizabeth at the funeral if she can still visit Ella, and Elizabeth replies "Of course, she's your sister." We find out in the series finale that the relationship between Elizabeth and Rachel has improved significantly since then. Rachel is doing her under-grad at Duke, where Elizabeth works, getting a deal on her tuition thanks to her stepmother. Elizabeth also comes with Rachel to Chicago for her med school application interview, appearing to be very supportive and proud of her step-daughter.
There is also the fact that even though she's doing her under-grad in North Carolina, Rachel wants to go to medical school in Chicago, where her father spent his entire medical career.