Most obviously, the senior staff of The West Wing, which goes so far as to mimic a nuclear family with the President and Leo representing the parents, Toby and CJ the older siblings, and Josh and Sam the younger ones.
Made explicit in "Lies, Damn Lies, and Statistics":
Josh: He [the President] thinks of you like a daughter, C.J.
Also, in "Two Cathedrals", the President says the following (to God, no less):
"What was Josh Lyman, a warning shot? That was my son. What did I ever do to yours but praise his glory and praise his name?"
Charlie is Bartlet's adoptive son in all but legal terms:
Sorkin likes this trope. The characters on Sports Night also act like this.
In Happy Endings this trope is illustrated often almost to the point of Deconstruction with how much time the characters all spend together. The biggest proof is illustrated in the main theme of the first season-the friends all staying together despite Alex running out on her and Dave's wedding-both of them care too much about their friendship family to mess it up. Likewise, while Dave and Alex are still adjusting to being friends, and fighting a lot, the other four are willing to go out of their way to do things twice-once with each of them, such as having a meal or watching a movie. In season 3, Penny's mom really shines a light on it.
Dana: Well I think its adorable how much time you guys spend together. You're practically attracted at the hip like those conjoined prostitutes I saw on Real Sports.
Big Dave: They're also power lifters.
Max: I wouldn't say we spend that much time together. I mean, just breakfast 4-5 times a week before work.
Dave: And drinks during the day most days-not everyday! But definitely every evening.
Penny: And sure we always deliver news in person.
Boyd Langdon from Dollhouse considers the people and staff of the LA house to be his family, even after revealing himself to be the Bigger Bad.
Sylar: Peter, you stayed? Peter: I wasn't going to leave you...
The Carnival, of Season 4, can be seen as this. Even Samuel, their leader and the Big Bad, seems to genuinely care for their safety and well-being. Granted, he isn't above murdering them if they stand in his way, but when he does, he clearly feels bad about having to do so.
This trope was done with the NewsRadio ensemble quite early in developing the dynamic, with Jimmie James eventually becoming the defacto father figure, to eccentric and near ridiculous extent.
Despite being barely able to tolerate each other, the main characters of Red Dwarf certainly fit this trope. The canonical example comes in "Terrorform", where Starbug is trapped in Rimmer's subconscious. Since Rimmer loathes himself, he is being tortured by a psychological demon, and the rest of the crew have to get him out. The episode's climax comes when the crew manage to convince Rimmer that they love him, which resurrects the warriors Self-Confidence and Self-Respect to defeat the demons and free the ship. Once it's over...
Rimmer: You really didn't mean any of that, did you? All:(in unison) ... No.
"The Last Day" has a rare genuine Friendship Moment, with everyone getting drunk together and reminiscing when Kryten tells them this is his Last Day to Live. On learning that the problem is his incoming replacement, who won't take no for an answer and will be prepared to use violence, they refuse to give him up.
Kryten: You would gamble your safety for a mere android? Is this the human value you call "friendship"?
Lister: Don't give me the Star Trek crap, it's too early in the morning.
The staff of Sacred Heart in Scrubs are constantly said to be "like a family."
Any Doctor Who companion(s), ever, even if they don't always get along, there's a certain bond. In "Journey's End" they are even given a name: The Children of Time.
Also in Journey's End, the Doctor and all the companions he's ever had up to that point in the revival series - Rose Tyler, Captain Jack Harkness, Martha Jones, Donna Noble, Sarah Jane Smith, Jackie Tyler, and Mickey Smith - pilot the TARDIS together to bring the Earth back home in an intense sequence that has moved many a fan to tears.
Sarah Jane: You know... you act like such a lonely man. But look at you! You've got the biggest family on Earth!
Brought up again in "The Wedding of River Song". After an entire series deconstructing the idea of the Doctor - that he hurts people, that he makes them scared, that he ruins lives, River shows him how all the universe has responded to her call to help him. Not just past companions, but anyone he's ever touched for the good.
The regular cast members of Jon Pertwee's run as the Doctor in the early 1970s ended up becoming known as "the UNIT family" (after the organisation many of the characters worked for) precisely because they became incredibly close to one another off-camera. The death of Roger Delgado, who played the Master, in 1974 was one of the key motivating factors behind Pertwee's decision to leave the role.
Eleven considers the Paternoster Row gang - Vastra, Jenny and Strax - to qualify as well, since they were there for him when he needed it after the loss of the Ponds.
The original CSI: Crime Scene Investigation team has been entering this trope over time. The season nine premiere only made it explicit, with even The Spock, Gil Grissom, calling the team his family. In return, more than one team member has stated they think of Grissom as a father figure. Catherine also acknowledges it when she walks into Grissom's office and sees Sara — as Nick and Greg walk in behind her, she hugs Sara tightly, looks around, and says, "At least we can all be together."
CSI NY is much the same, with all of them acting like family. Danny and Lindsay got married, Mac is a father figure and Lucy's godfather, Flack and both Mac and Danny are like brothers, Mac is a father figure for Hawkes sometimes, and first Stella and then Jo were close to all of them.
Team Gibbs in NCIS, made abundantly clear any time any one of them ends up in some kind of trouble. The Season 4 premiere episode "Shalom", in which Ziva is suspected of being a Double Agent and goes on the run from the FBI, provides a particularly clear example, as do the first two episodes of Season 6. Which makes the ending of Season 6 all the more poignant.
The Mall Rats in The Tribe have this sort of relationship. They are one big, dysfunctional family - complete with marriages, affairs, power-grabs, friendships, substitute parental figures and siblings both literal and metaphorical. They frequently had issues and disagreements in the group but would come together as a tribe when they needed to.
Friends was described by one critic as a show about a bunch of young adults finding a replacement family for their own, dysfunctional ones. Lampshaded by a Guy of the Week of Phoebe's whose minor flaw was his incessant psychoanalysis of the group. The gang through the ten year run support each other in every circumstance from Ross's divorces to Phoebe's surrogacy and Joey's acting career. They operate as a complete, exclusive unit, and although there are several times, like Ross and Rachel's break up, Ross's marriage to Emily and Chandler and Monica moving away, when they worry the group might split up, nothing's strong enough to break them. The cast of Friends could be considered as a Real Life version, too.
Priority Homicide from The Closer has become this over time. In the first episode, the entire squad requested transfer out of Brenda's division. In that season's finale, the entire squad threatened resignation when the misogynistic Captain Taylor lodged an IA complaint against her. They still take issue with her sometimes, but God forbid anyone tries to get rid of her. From the Season 3 finale:
Sgt. Gabriel: For keeping the team together, despite some pretty hefty pressure, and, um, for trusting her instincts — about us too, by the way — and, um, for how she always works so hard to get her man. I say hail to the Chief. The Squad: The Chief!! Brenda: Well, that was, um, well, y'all are a little bit like my... a little like my own... Oh, for heaven's sakes. Thank you, and right back at you. All of you.
Finch and John Reese in Person of Interest certainly count. Initially starting out as employer and employee, they have become pretty much best friends and will do anything to protect each other (especially Reese to Finch, bodyguard blocking him out of the range of gunfire, withstanding torture to protect him and otherwise just being there to make sure his friend is safe) it's pretty heartwarming stuff
The main crew of Pushing Daisies: Olive and Chuck are like sisters, and when Chuck comments on Ned needing to reconnect with his family, he says that Chuck and Olive are his family. Emerson is a lot more reluctant to express affection for the others, but it's there.
The Merry Men in Robin of Sherwood or the outlaws in BBC's Robin Hood (or indeed, any retelling of the Robin Hood legend that includes all the Merry Men). In the case of the BBC version, this is more true in the first season. In the second season Allan turns traitor and begins working for the enemy, but in the same episode he has his Heel-Face Turn and returns to his true companions, and outlaws Will and Djaq opt to stay in the Holy Land together as the others return to England. The third season has less emphasis on the outlaws, and newcomers Tuck and Kate never achieve the closeness of true companions that the previous incarnation of the gang did.
Subverted on The Shield: At the start of the series, the Strike Team are true companions, with the team members considering each other brothers and Vic Mackey the ultra-loyal father of the group. Once Vic shoots Terry Crowley in the face and tells Shane Vendrell to pretend it never happened, to the point that Vic refuses to let his guilt-striken conspirator in the crime ever mention it in his presence, it all falls apart. By the end of the series, everyone is dead or has been betrayed by Vic.
The team on Criminal Minds is practically the definition of this trope.
Hotch is Mom, Gideon or Rossi is Dad, Morgan is Older Brother, Emily (later Alex) is Older Sister, JJ and Garcia are the Younger Sisters, and Reid is Little Brother (or the Baby, since he is the youngest and everybody always wants to protect him). Never, ever mess with a member of the BAU, because the rest will hunt you down and kill you dead.
The team interacting with Rossi in his first few episodes always seemed to me like a group of suspicious teenagers getting to know their stepdad when they're not quite over Dad leaving yet.
Done particularly well in "100", when the entire team refuses to go along with the witch hunt against Hotch for how the Foyet case ended up, and gather around Hotch and Jack at the end in a show of support.
Because they are a working family, it makes JJ's departure even more heartbreaking. It's like the BAU's hearts have been ripped out. If you didn't cry at the end of "JJ," you're no fan of the show.
Morgan refers to Hotch and Rossi as Mom and Dad a few times.
Murphy Brown: "We really ARE a family. Only a family could be this messed up!"
The New Directions kids spend a season getting to this. The group as constituted by episode 4 consists of 5 people from the social margins (Rachel, Kurt, Mercedes, Tina, Artie) and 7 popular kids from either the football team or the Cheerios (Finn, Puck, Mike, Matt, Quinn, Santana, and Brittany), with the latter three being there explicitly to sabotage the group. Finn, Mike, Matt, and Brittany mix in with the marginals easily, and Quinn does after getting bounced from the Cheerios. For a lot of the time, the biggest divide in the group is that for several stretches Finn is the only one who likes Rachel at all. The biggest holdout is the replacement Alpha Bitch Santana, who, despite liking performing, takes a long time before she'll admit to it in public, and still treats a lot of the team with contempt. But by the finale, when it looks like things might be over, she's crying like everybody else.
Kurt: Now get out of here. And take some time to think whether or not any of your friends on the football team would have done that for you.
Their bond is most clearly seen when Jesse humiliates Rachel, the most abrasive of the group. All of the boys prepare to take him and his team out. Including wheelchair-bound Artie.
Kurt: Mr. Schue, Rachel's one of us. We're the only ones who get to humiliate her.
And in "Furt". When they find out Kurt is being bullied, the rest of the guys in the club confront the bully, complete with several punches to said bully's face. Everyone in the club has been openly hostile to Karofsky (the bully) ever since.
And again in the season two episode "Rumours," where, after serious gossip threatens to tear the club apart, they ultimately buy Sam's guitar back from the pawn shop and support him via song.
Brittany beautifully lampshades it in the season two finale:
Brittany: I know that all the kids in Glee club... they fight, and they steal each other's boyfriends and girlfriends, and they threaten to quit, like, everyother week. But weird stuff like that happens in families.
Santana: Yeah, well, this is a club. This is not a family.
Brittany: Okay, well, family is a place where everyone loves you no matter what, and they accept you for who you are... I love them. I love everyone in Glee Club. And I get to spend another year with everyone I love, so, Iím good.
The cast themselves seem to be very close in Real Life.
Community: The study group. Without question or doubt.
In the Christmas special episode, one of the members of the study group isn't respecting the other members' diverse religions. One of the other characters calls the group a family while pointing out why this is wrong. At the end of the episode, the gang fight a bunch of homoerotic school bullies together. Afterwards, they return to their holiday party. All of the characters are battle damaged and sit around smiling at each other while singing nondenominational carols. Awwwww.
The second half of the first season plays with the concept. One episode has someone attempting to join the group, examining their resemblance to a clique. Another episode deals with whether or not it's incest if "family" members are dating each other.
Supernatural: As brothers who would sell their souls for one another, Dean and Sam started out this way and have added Team Free Will to the roster. They so much consider Bobby family that in season six, when Dean had to think of a name for a baby he and Sam were taking care of, he chose Bobby instead of John (his actual father.) Factor in Sam calling Bobby 'sir' (what he called John) and Bobby's probably more of a father than their real father. Dean tells Castiel he's like a brother to him in later seasons.
When Dean meets a version of himself from five years in the future in 5x04, one of the clearest signs that Future!Dean has changed for the worse is that he sends a group of his comrades and friends, including the emotionally-broken Future!Castiel, into a situation to act as an unknowing distraction and ultimately get killed. Made worse by the fact that it's implied that Castiel, at least, knew exactly what Dean was doing but went along with it anyway. Present!Dean is understandably horrified by this.
Castiel rebelled against Heaven to help Dean and Sam. Bobby considers them like sons to him, and in season seven episode "Death's Door" says to his abusive father in a memory while he's dying:
Bobby: I adopted two boys, and they grew up great. They grew up heroes.
The Pretender skews this one six ways from Sunday. Jarod, Miss Parker, Sydney, and Broots are true companions despite the fact that Jarod broke free from the Centre, Parker is hunting Jarod (while still being kind of in love with him), Sydney is everyone's father figure (while still being morally suspect as to which side he's on - the Centre or Jarod's), and Broots is the resident Butt Monkey. But professional loyalties aside, they all agree that they're kind of family. Demonstrated explicitly in "Donoterase" when Jarod allows himself to be captured by Lyle and Bridgette rather than leave a wounded Parker behind.
Silent Witness: Leo, Nikki and Harry in the later series. Leo calmly tells Nikki and Harry that they are as important to him as his wife and child.
Joss Whedon loves this trope. In an interview on a Firefly DVD extra, Joss said that one of his favorite themes is "found family". The crew of Serenity in particular will do anything for each other. In fact, they form a sort of surrogate family, with Mal as a definite father figure, Inara as mother (insert meaningful joke about her profession here), Zoe as the eldest daughter (taking responsibility for running things), and Jayne as the rebellious teenager. They are a family, right down to sibling rivalry, petty squabbling over chores, complaining about being sent to find parts in a junkyard instead of going shopping... River even assures Simon that "Daddy will come get us." Who eventually does come? Papa Wolf Mal. This exchange after Mal and crew save River from being burned at the stake in the Big Damn Heroes moment named the trope:
Mal: Cut her down! Patron: The girl is a witch. Mal: Yeah, but she's our witch. (KA-CHINK!) So cut her the hell down.
Angel neatly summarized the concept in the episode "Awakening":
Angel: We've been pushed to the edge so many times; done things we were sure could never be forgiven. But we're always there for each other when it counts. We've never let the darkness win. And it's not because of the Powers That Be or the super strength or the magical weapons. It's because we believe in each other, not just as friends or lovers, but as champions. All of us, together.
In the season 3 episode where after Connor is kidnapped, Wesley is outcast. Angel and the remaining Team Angel go on a mission to win back Gunn's soul because: "We're not losing another member of this family."
The Scoobies have formed bonds that seem stronger than those of kinship, as pointed out in the episode "Family", when Tara's family comes to take her home against her will.
Farscape: The Moya crew sure qualifies. Certainly it's a very screwed-up example, but they're still true companions. In the first season, they were mostly thrown together (three prisoners who happened to be on the same ship, the pilot of that ship, the ship itself, an enemy fighter pilot who was accidentally captured, and a scientist who randomly fell through a wormhole and ended up in the middle of the escape attempt), and John several times had to stop some of the others (particularly D'Argo and Rygel) from abandoning the rest when they got themselves into scrapes. As the series goes on, they get closer and closer until eventually their one rule is "look out for the family, at all costs." As new characters (Chiana, Stark, Jool, Noranti, and Sikozu) join the crew, this bonding process takes a while to set in, but eventually they are integrated into the family as well. However, the initial coldness might have contributed to Sikozu's eventual Heel-Face Turn, as Scorpius welcomed her with open arms, while the others (particularly Chiana) took a while to warm to her.
The relationship between Pilot and Aeryn is strange and distinct enough to warrant further elaboration. They, more than the others, change the most in the early episodes: Aeryn from a soldier in a galaxy-spanning military dictatorship, Pilot as essentially a slave to that dictatorship. This is demonstrated in an episode where the science-y members of the crew (John and Zhaan) are unavailable, so Aeryn has to do testing on Rygel on her own, complaining that she is unsuited for this kind of work—only for Pilot to admit that he has difficulty understanding complex sciences, too. Later on they share DNA, causing their bond to be made physical. Aeryn is often times the only one who sees Pilot as a distinct being rather than an offshoot of Moya. This makes the episode "The Way We Weren't" all the more painful, as it reveals the dark past of both of them, and puts serious doubts that their relationship will survive the revelation that Aeryn was part of a firing squad that killed Moya's former Pilot. However, the two manage to re-bond and forgive each other and themselves for their past sins.
Stargate SG-1 could be said to epitomize True Companions with its flagship team. This sense of family is accentuated by the fact that each character considers the team to be almost the only family they have: Jack is divorced and his son is dead, Daniel was orphaned in his childhood with no siblings and a distant grandfather, Sam lost her mother as a teenager and is distant from most of her surviving family, and Teal'c was forced to abandon his family when he chose to rebel against his tyrannical "god" (after also losing both parents to violence when he was young). Throw together these depressing backstories, add new trauma and hardship, and you get one of the strongest bands of True Companions ever. This is addressed as early on as the thirteenth episode, when Daniel is presumed dead and the team acts as his family during and after the memorial service.
Jack and Teal'c both serve in big brother roles for the team. Jack is the sarcastic, teasing kind who makes up silly nicknames and mocks his enemies, but will do anything and everything to help if one of his "kids" is threatened, whereas Teal'c is the stoic, protective type who serves as a source of strength and dependability for the others.
Daniel and Sam are the "science twins" of the team, both having a tendency for Techno Babble and being the most likely to come up with a solution for their conundrum (Daniel's expertise being the soft sciences, while Sam's is the hard sciences). Their relationship hits off the best, and before long they are Like Brother and Sister.
Also of note is the fact that one of the primary reasons for Sam and Jack's mutually-self-denied love is the fact that addressing it would require breaking up the team.
General Hammond, who is A Father to His Men; General Landry later takes on this role, to a lesser extent.
Jacob Carter, Sam's father, who initially has a difficult relationship with his daughter but ends up becoming close with all the members of the team.
Dr. Janet Fraiser, the chief medical officer at the base and a close friend to the members of SG-1.
This is one of the reasons why Sam and Jack (especially Jack) initially have a hard time fully accepting Jonas Quinn, who replaced Daniel for a year, as a member of the team, despite the fact that they don't have any honest objections to the guy.
It then gets shaken up further when Jack is promoted away and Cameron and Vala join the team. Cam and Daniel end up treating each other like brothers (or at least very close friends) while Sam and Vala become like sisters, and Vala and Daniel pick up the UST mantle where Jack and Sam left it.
Samantha Carter: "We were a team. No one can even begin to understand what that really means."
General Hammond to his granddaughter, when Daniel is missing: "I'd love to come see you in your school play tomorrow night, but can't. Well, a very close friend of mine is lost, and he needs my help. Yes, he's a very close friend."
Note that General Hammond is very fond towards his grandchildren, and has them at a higher speed dial than he does the President of the United States. Yet he still thinks it's important enough to rescue Daniel.
General Landry (before a rescue mission): "Teal'c is family. I don't like people screwing with my family."
Cameron Mitchell, to Vala: "Now you know the hard part about being part of this team is not risking your own life; it's watching your friends take chances with theirs. Congratulations. Now you really are one of us."
It's the same in the spinoff series Stargate Atlantis. Especially as the expedition members are sent to another galaxy with little hope of returning home. The main cast, (John, Elizabeth, Rodney, Carson, Ronon, and Teyla) grow extremely close and despite disagreements depend on each other utterly.
A particularly tender moment occurs when Teyla tries to come to terms with returning to active duty after her son is born, since that could mean leaving her child without a mother (the father is currently missing.) Sheppard reminds her that her child has a family on Atlantis if anything ever happens to her. Awww.
Possibly the best example from the series:
Sheppard: You, Elizabeth, Ronon, Carson, even Rodney, are the closest thing I have to a...
Teyla: A family?
Sheppard: (nodding) I'd do anything ... for any one of you. If I had to give up my life the way Ronon was going to, I would.
Subverted in Stargate Universe: From very the start of the series, the people stranded aboard the Destiny are anything butTrue Companions, and it doesn't get much better either...
Every version of Star Trek has this, from the original to the latest incarnations. This is apparently also Truth in Television as the writers are inspired by real life crews and teams who became close through mutual experience. Even more, the cast and crews of the various TV series have been working together for roughly 10-20 years and have come to regard each other as an extended family in Real Life. The greatest example of this is how Avery Brooks has become like a second father to Cirroc Lofton, mirroring their roles as father and son on TV. Although it took a decade or two, William Shatner and Leonard Nimoy eventually developed the same friendship Kirk and Spock share, if not to quite the same intensity.
This was never better exemplified than in the original series episode "The Empath", where each member of the Power Trio was bound and determined to sacrifice himself to save the other two. McCoy eventually wins that particular argument - with a hypospray. The more things change, the more they stay the same...
Star Trek: The Next Generation had a bit of this going on, particularly during the first season, before the characters had worked each other out. Riker was uneasy about their second officer, Picard had to tell people not to let him "make an ass of himself" around children (and shouted Wesley out in the very first episode, thus enraging Wesley's mother with whom Picard already had an uneasy relationship), Worf disliked everyone (but especially Data), and Troi and Riker had Uncomfortable Ex's syndrome. But within a matter of episodes (and fairly ridiculous episodes at that) it became obvious that they'd all die for each other.
Star Trek: Deep Space Nine and Star Trek: Voyager both feature crews of people who don't even want to be on the same ship/station with each other, but over the courses of each series have wound up going as far as disobeying orders to save one another.
Michael Westen is closer to Fiona and Sam than he is his actual family, having placed his life in their hands more than once in their long history as spies. Over the course of the show, he has to learn to to re-relate to and trust his mother and brother Nate as well as he does his friends. And, as many episodes including season finales have shown, you do notmess with Michael's family or his friends.
Michael: Fiona is not my past!
Madeline certainly sees things that way. After firmly rebuffing Nate's attempts to move her from Miami to Las Vegas, she invokes Sam and Fiona as well as Michael to justify why.
Chuck: The Operation Bartowski team will save America; and each other; no matter what.
The non-spy employees of the Buy More could qualify as well. They may hate their jobs, but they stick by each other and the store, especially when it's threatened by the employees of the rival Large Mart or even other Buy Mores.
Boston Legal: Crane, Poole & Schmidt, especially the litigations department. They're a family; a very dysfunctional family, but a family nonetheless.
Season Two added Ames (who eventually ends up in a sort-of father/daughter relationship with Token Evil Teammate Gurerro) and Ilsa Pucchi (although she's a bit more distant from the others, being in essence their employer)
On Castle, he, Beckett, Ryan, and Esposito have formed one of these, to the point where Castle offers to let Beckett stay at his house after a psychotic serial killer blows up her apartment.
After Montgomery dies, Beckett insists to Castle, Esposito, and Ryan that no one outside "this immediate family" find out the true circumstances surrounding his death.
Very heartwarming example later when Beckett (who is in a relationship with Castle at this point) considers breaking the law to save his life. Esposito warns her not to try as she would not succeed but assures her "I know how you feel about the guy. I love him, too."
In The Vicar of Dibley, Geraldine motivates her friends to work towards stopping the destruction of the village for a new reservoir by saying that after being rejected by four parishes, the "mildly bizarre and dangerously odd" parishioners of Dibley became her family.
Ted, Marshall, Barney, Lily and Robin- despite being very different people- form one of these in How I Met Your Mother. They're also somewhat unique in that their group's immortality is ensured not because of the Plot Immunity and Like You Would Really Do It that accompanies most of these examples but because the story is set in the future, where the comments of Future!Ted and his kids makes it clear they are all still best friends (e.g., referring to them as "Aunt" and "Uncle", as well as through Flash Forwards and other clear spoilers). He admits that yes, by the year 2030 they had all drifted apart a little bit in the sense that they weren't always sitting together in the booth at McLaren's every single night, but as he puts it, "Our booth was wherever the five of us were together."
The defining moment of the group's True Companionship? When Lily and Marshall are trying to decide who should be Marvin's godfather/godmother and end up naming all three of their friends as Marvin's godparent (or guardian in case something should happen to Marshall or Lily).
Lily: "No matter what happens I want Marvin to stay in the family"
On Sex and the City, the Four Girl Ensemble of Carrie, Samantha, Miranda, and Charlotte explicitly consider themselves as family. The various men that they date and marry in the series never enter the group in a meaningful way, although Carrie's Flamboyant Gay friend Stanford Blatch seems to have part-time membership.
Big said it best when he was telling Charlotte, Samantha and Miranda how much they mean to Carrie: "A guy would be lucky to come in fourth."
There's also the Four Girl Ensemble of Susan, Bree, Gabrielle and Lynette from Desperate Housewives. Note that Edie is clearly not a part of this group, proven for good when she tried to blackmail Bree in Season Four, causing the other ladies to stand by Bree and basically kick Edie off of Wysteria Lane. By contrast, when Katherine killed her ex-husband to protect herself and her daughter, the four quickly covered for her, making it clear they saw her as their true friend.
Noah's Arc: Noah, Ricky, Alex and Chance, who see themselves as family and explicitly state that nothing they go through can break their bond.
Inspector Lynley and his partner DS Barbara Havers are this to each other, explicitly so — it's made quite clear that they are easily the most important person in each other's lives.
Both subverted and played straight on Prison Break. Subverted with the original group that broke out of prison in season one, as seen during season one and two a number of times, including but not limited to T-Bag's hand being cut off, Tweener and Haywire being left behind, and Michael trying to steal the money out from everyone except Sucre. Played straight in that Michael, Linc and Sucre are true companions in season one; LJ and Sara are added to in season two. Subverted again in season three, as Mahone and Michael (much less the rest of the group) have no problem backstabbing each other while trying to break out of Sona. Played straight in early season four (as they're on their way to becoming one) and then subverted when the group splinters in the later part of the season. The direct-to-DVD gives us the basic group, seen in the season four finale at Michael's funeral, of Linc, Michael, Sara, Sucre, and Mahone.
The Misfits become true companions, albeit through shared culpability for multiple murders.
Richie, Ralph, Potsie, and Fonzie on Happy Days. Regardless of when Fonzie jumped over a shark, the show jumped the shark when Richie and Ralph left the cast, and Potsie was phased out and forgotten.
Julian, Ricky, and Bubbles from Trailer Park Boys. Their familial devotion to each other is one of the reasons it is possible to sympathize with these criminals. The next closest member to their group would be Ricky's father Ray, but it is also made explicit that all of the residents of the Sunnyvale Trailer Park have a close bond to each other and that is one of the reasons it is not such a hellhole as it appears. Even the antagonists Mr. Lahey and Randy can be counted on to work together with the boys sometimes. Unfortunately this trope doesn't apply to Cory and Trevor no matter how much they want to be accepted.
The relationship between the members of S Club 7 was portrayed this way on their show. They all thought of each other like family, were always there for one another, and became deeply depressed in the episode where Paul left the band. The relationship between the band members in real life, however, was a completely different story.
The Knights of the Round Table are very much true companions. Arthur often talks about the bond the knights share and how special and unique their relationships are. There are also numerous scenes where Arthur will try to face something dangerous alone only to be reminded by his knights that they will always be there for him.
The original Battlestar Galactica has the trio of Apollo, Starbuck and Boomer who share the closest friendship amongst the rest of the pilots. Sheba was included about half-way through the show.
In fact, almost the whole main crew on the Galactica are close to one another. They even take turns looking after Boxey.
Once Upon a Time: It's not quite as blatant as most examples, but this seems to be the relationship that has formed between, at the very least, Snow, Charming, Red, and Grumpy, and possibly also including the other dwarves and Granny.
The survivor group in The Walking Dead counts, definitely by the start of the third season. Eight months spent together refining their skills and not losing anybody makes them a close-knit family, even despite all the drama they've put each other through. Makes it all the worse when they lose Lori and T-Dog; Glenn outright refers to them as family while digging their graves. Furthermore, in a more positive sense, the reunion of the previously-missing Carol with everyone shows this trope in full effect.
The Golden Girls group mentioned being family several times,including to Rose's daughter,who didn't get the idea at all.
The Smithsonian gang in Bones. A few seasons in, it becomes obvious they'd do anything for each other.
This does not only include the main characters, either. It becomes very clear very quickly that several recurring characters, such as Caroline Julian and the "squinterns" (Vincent, Daisy, Clark, Wendell, Arastoo, Fisher, and Finn), are included in the group when they're around, as anyone from the main group will end you if you hurt any of them.
Artie, Myka, Pete, and Claudia from Warehouse 13 are referred to as a family in the Christmas episode "The Greatest Gift".
The "seven stranded castaways" on Gilligan's Island. If one of them's in danger, the other six rush in to help. If one is (always wrongly, of course) believed to have died, the other six will be beside themselves with grief. And while they may not be able to get off the island, they are actually quite adept at surviving whatever obstacles could cause them to perish there. In the end, the answer to the infamous question, why don't they Just Eat Gilligan, is easy. Because they love him.
All three generations of Skins are based around these.
The members of the Circle in The Secret Circle, but some more reluctantly than others. (Faye in particular wasn't much of a team player at first.) Of course, in their case they don't really have a choice, since their powers only work when two or more of them are together.
The main characters of Grey's Anatomy, especially the original 5 interns and Team Mom Bailey, though two of them were written out; the remaining 3 and Bailey have become close to the other new main characters.
In Never Wipe Tears Without Gloves Paul (and eventually several others) refers to his group of friends as "the family". As the story progresses it becomes increasingly obvious that they have a much stronger bond between them than any of them do with their biological families.
It's a Crowning Moment of Heartwarming that Paul welcomes every insecure gay man he meets to join the group and names them members of the family right from the start.
The rebels in Spartacus: Blood and Sand. Nicely illustrated in a scene late in the final season, when the remaining rebels remember their fallen comrades.
HouseOfAnubis- Sibuna definately qualifies. Sure they tend to bicker and tease each other a few times, but there is no denying that they are an extremely close group, who will never turn their backs on one another. It spoke a lot when Nina needed help, and the rest of Sibuna automatically jumped at the chance to help her, even after she protested in concern for their safety.
Though not as close, he entire house qualifies. They bicker and have a ton of drama like any group of teenagers. But if one of their own are threatened by an outside force, or have a problem that involves them all, they all join together to fight it off. The best example is probably when Patricia, Alfie, Eddie, KT and Fabian were all expelled from the school. Joy, Mara, Willow and Jerome all immediately vowed to help them get back into the school, and even talked about taking it to court for them. It certainly helps that their families aren't the best, and because they live together, they are basically family.
Smallville: The JLA in general in this, however in Season 10, Clark, Chloe, Oliver, and Lois are this to a major degree. By the end of the season Tess has eventually ended up as this as well even if the others do have some hesitations about her. By Season 11, she's fully redeemed herself to all of them, including Lois (the one who still had reservations the latest into S10). Really, the main group featured in "Fortune" (Clark, Lois, Chloe, Oliver, Tess, and Emil) are the closest of all of the JLA members, and are the ones most likely to do whatever they can to help the others.
Team Arrow forms a close bond, with Oliver, Diggle, and Felicity at the core and the occasional inclusion of Roy, Lance, and Sara.
One Tree Hill: The "core five" (Lucas, Nathan, Peyton, Haley, and Brooke) are this primarily. The group expands a bit in early seasons to include Mouth and Skills, and then over the next few seasons expands further to include Millie, Julian, Clay, Quinn, Chase, and, in the last season, Chris Keller.
It should be absolutely no surprise that by the end of the first episode of The Musketeers, D'Artagnan, Athos, Porthos, Aramis and Constance clearly fulfil this trope (with added Papa Wolf Treville). Quite frankly, anything less would be a betrayal of the source material.