"I don't have a cellphone. I just hang out with everyone I know, all the time. If someone wants to get hold of me, they can just say, 'Hey, Mitch,' and I will turn my head slightly and say, 'Yeah, what?'"
In some ensemble shows (especially the Sitcom), the main characters form a tight social circle. They all know each other, and do everything together.
In other ensemble shows, the main characters form a really tight social circle, so tight that it seems more like an exclusive club than a bunch of friends. Any other friends they have are never as close, and will inevitably be introduced to the entire group. The characters will panic if one of them hangs out with an outsider for too long, fearing that this will destroy the circle. Any gathering they attend consists of them and the 24 Hour Party People.
In still other ensemble shows, the main characters form a really, really, really tight social circle, so tight that other characters barely exist. Outsiders either vanish without a trace after one episode, leave for petty reasons like "man hands", leave because they can never be part of the group, or are eternal enemies of the circle.
It's almost as if the main characters had some special criteria they use to exclude others, like whether the actor playing them gets top billing or not.
For ensemble and sitcom shows, there's usually a few justifiable reasons to keep the main cast as a closed group of friends for the story. Keeping the amount of main characters limited helps keep the audience focused on the main characters instead of having everyone coming into the scenes all at once and confuse or distract the audience. It also keeps production costs down since it's easier to write and direct for a group of 6 people than to do the same for a much larger group. When done right, the audience may not notice or care that the main cast of characters are hanging out with each other more than other people. When done poorly, it can make the main cast look like they can't be friends with anyone else but each other.
Most shows that have this make it an integral part of the show, or at least do a Lampshade Hanging about it.
Compare with Cool Loser. Possibly the result of an Economy Cast or Friendless Background. A limited attempt to avert this is Social Circle Filler.
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Anime and Manga
Two of these exist in Kodomo No Jikan. Rin, Mimi and Kuro (and, depending on what they're doing, Rin will drag Aoki into it) make up one, Aoki, Houin, Shirai and Oyajima (the only four named teachers, and at times, the only four teachers) making up another. Aoki was shown having outside of work friends once, really early on. They haven't shown up again. When there's even other teachers in existence (sometimes nameless, non-student people will be seen in the Teacher's Lounge, but not normally) the main 4 are treated like the only ones in existence. The other students are never even named.
In Pretty Sammy, both Misao and Sasami (despite the second being supposedly more social) only hang out with each other and their parents.
In Ranma ˝, ancillary characters are hardly ever named and never seem to play any significant part of the main cast's lives. If anything, they're just admirers. The main cast (The Tendo and Saotome families, the Chinese Amazons, and the Fiancee Brigade) and the second-string characters all seem to be a self-contained unit. This is understandable, as regular humans are too fragile to hang out with this bunch without getting hurt.
Sailor Moon did this too. One early subtext for the television show alludes to each character's situation making it hard for them to make friends, despite later seasons having them meet new people every few episodes; most of the new people they met were Victims Of The Week who never showed up in more than one episode. The only normal friends any of them have are Naru and Umino.
Usagi seemed to have a broader social circle in the first season, especially if you count her family and teacher. Almost all of these characters were reduced to one token appearance per season (if they showed up at all) from season 2 onward, with the senshi hanging out with each other pretty much exclusively. This is reinforced by the fact that almost every episode has them becoming good friends with the Victim of the Week but after the episode ends, said person is never seen or heard from again.
One episode during the opening Filler arc of Sailor Moon R made this especially apparent. The episode has the cast decide to put on a play. No thought was given to casting anybody from outside of the five Sailor Senshi, Mamoru, Naru, Umino, and the two unknown villains.
Problematic in Yes! Precure 5, as the small circle of friends is identical to the team of Magical Girls. Urara explicitly has no other friends, Nozomi and Rin are overly reliant on each other, and Karen's personality could push people away, but there's really no good explanation for why Komachi never hangs out with anyone else.
Suzumiya Haruhi. No one appears to have any friends outside the SOS Brigade except Kyon (who has exactly two) and Mikuru, whose friend Tsuruya pretty much gets honorary SOS Brigade membership. Somewhat justified in that Haruhi's an abrasive Cloud Cuckoo Lander, Kyon actively seeks boredom, and the rest of the Brigade is technically just there to keep an eye on those two (though they warm up to each other eventually), and have variousotherissues that mean they lack any pre-existing social circles.
Azumanga Daioh is guilty of this: Chiyo, Sakaki, Osaka, Tomo, Yomi, Kagura, Kaorin, Yukari, and Nyamo all go to Chiyo's summer home. That's the entire main cast. And two of those are teachers. With the exception of Kaorin (who has at least a few friends from her other class and the clubs she attends) and Chiyo (who mentioned a friend in America and keeps in touch with her elementary school friends), it seems that the only friends that they have are named above. (That counts the teachers, by the way).
Then again, most of those characters aren't the type to have wide social circles. Sakaki tends to scare people away by accident, Osaka lives in her own little world, Chiyo has a massive age difference with her peers that makes it difficult for her to relate to them, and it's implied that Tomo and Yomi are doomed to be each other's only real friends due to their personalities. As for Nyamo and Yukari...they're basically the "peek into the future" of what Tomo and Yomi will be like. Nyamo does eventually come to the conclusion that she needs to fix this and at least start dating people.
In Mahou Sensei Negima!, friends that are not directly related to Ala Alba fade in importance until they're barely there at all. It's also noted in story by some of the other classmates feeling somewhat alienated. Ala Alba is actually an exclusive club, though.
In Amanchu!, none of the main characters seem to have any friends outside of the diving club. They are mainly seen hanging out with each other and are hardly ever seen interacting with any of the other students. Hikari might be a bit of a loner, despite her open, friendly demeanor, but Futaba is seen to have left behind quite a few friends in her home town, so she should be able to make new ones. The twins Ai and Makoto also don't seem to socialize much either and are mostly seen together.
Hinagiku, Miki, Risa and Izumi of Hayate the Combat Butler are all friends, and are almost always seen interacting with each other exclusively. As the story continues, the social circle expands a little to include Hayate and Nagi and eventually several others, but still rather limited.
Isumi, Nagi, Wataru and Sakuya share the same dynamic, being childhood friends, they are hinted to have grown up together, mostly because their parents were all friends/family as well, and have limited interaction with anyone else. Isumi is a Cloud Cuckoo Lander, Wataru spends all his time not at school trying to keep his business running, and Sakuya goes to another school supposedly. Nagi started off being a Hikikomori but has begun to start expanding her social circle because of Hayate's influence.
The characters of Higurashi no Naku Koro ni have no friendships outside of their gaming club, possibly because no one else likes playing when cheating is part of the game. After new guy Keiichi is welcomed into it, he makes no more friends in town.
THE iDOLM@STER - The girls aren't shown to have any friends aside from the 765Pro ones. The only one who has a named friend is Azusa, but even then, Tomomi isn't seen or voiced during the entire show.
In Saki, most of the characters who are in their high school's mahjong team form a fairly tight-knit circle of friends, although some often end up becoming friends with rival players. It's somewhat lampshaded in Saki Biyori, when Hiroe and Kinue Atago, members of Himematsu's mahjong team and daughters of Senriyama's coach, Masae, sort their New Year's cards, and find that the largest pile is for the two of them and their mother(their father is apparently alive but has never been seen), prompting Hiroe to note that the three of them "have a lot of common acquaintances."
Attempted enforcement in the XY arc of Pokémon Special, as the group of traveling friends is explicitly trying to avoid other people in fear of Team Flare finding and killing them.
Averted by Spider-Man Loves Mary Jane — although the story focuses mainly on Mary Jane and her 'inner circle' of close friends, it's often established that Mary Jane herself is a popular and well-liked girl, so we will often see panels of her chatting to her other friends, some of whom (including a goth girl called Jessica) recurringly pop up every so often.
Played straighter with Mary Jane in the main comics. While some writers will remember to have her hang out with someone whom isn't Peter or someone she knows through Peter like a fellow actress or model, a lot forget. The Fridge Logic sets in when you begin to wonder why someone as outgoing as she is knows so few people.
Any number of superheroes especially in their personal lives. Clark Kent, for example, doesn't seem to have any male friends at all. He's shown occasionally socializing with Jimmy or Ron Troupe, but its not a close association. Everyone else is his various ex girlfriends, relatives, or coworkers. Even as Superman, his only close friends are Batman and Wonder Woman (he's much more formal with pretty much any other hero.)
There's also Pete Ross, Clark's best friend from Smallville, plus various miscellaneous (mostly one-shot) characters Clark hung out with in Smallville pre- and post-Crisis. Apparently, Clark's social circle in Smallville seemed a bit larger than in Metropolis...
At the beginning, Rudi used to meet many different friends, but later his social circle shrunk to Freddy, Bully and Heinz. And the Girl of the Week.
Justified in W.I.T.C.H., as they have little time for socialization that adds to other problems: Will suffers from severe trust issues since being betrayed by her previous social circle from her hometown when her parents divorced (she still has a childhood friend, but they now live in different towns), and is somewhat of an outcast due being a tomboy, her insane love for frogs and her tendence to react violently to perceived dangers or offences (her first encounter with Matt consisted in him offering to help with a wounded doormouse and Will punching his foot because she thought he was one of the bullies she had just chased away); Irma abrasive sarcasm tend to drive people away unless they're more perceptive (she found a friend in Martin about a year before the series, and Hay Lin was shown to be already her best friend. Both of them could see what was hidden under her sarcasm) or have a similar sense of humour (Cornelia); Taranee is quite shy and has trust issues almost as severe as Will (who coincidentally is her best friend) and opens up only if forced (the other Guardians), you go to her same dance school (Luke Pradd and Sheila Jensen) or have similar problems to the ones she had when she moved to Heatherfield (Will); Cornelia used to have a wider social circle, but her undeclared war with the Grumper sisters and the hurt from being separated from Elyon and her love story with Caleb ended up isolating her; Hay Lin, being the local Cloudcuckoolander, is avoided by most people unless they need her considerable skills in sewing and creating new outfits; finally, the girls have continuously humiliated the school bullies, and the other students may be scared of their revenge if they are friendly with the ones who keep them at bay.
Tamora Pierce's set of four foster siblings refer to themselves as a circle, get annoyed if one of them tries to make a Love Interest as a part of "the circle," and defensively mention that it's okay to have friends outside of "us."
The Baby Sitters Club became like this in later books but the early ones had them having friends outside the club.
Similarly, most of the Animorphs (particularly Jake) are noted as having friends in the early books, but as the series goes on, they apparently lose touch with said friends until all they really have is each other. Justified because of the whole "sole resistance against an alien invasion" thing.
Most of the main cast of Kill Time or Die Trying have few, if any, friends outside of the WARP club, and most spend more time with one another than with their own families.
Live Action Television
Friends is probably the most obvious example; the six friends barely seem to know anybody other than their families and each other. And their Girl of the Week, of course.
This was lampshaded in one episode. The main characters are all hanging out at Monica's apartment when someone knocks at the door. Everyone is stunned for a moment, and Phoebe actually counts to make sure that, yes, they're all already there. No one says anything out loud, but you can tell they're all thinking, "If we're all here, who the hell is at the door!?"
Another time, Monica and Phoebe were the apartment and the phone rings. Phoebe says it can either be Chandler, Joey, Ross or Rachel.
Yet another time, when Chandler suggests to Joey, Phoebe and Monica they have a surprise party for Rachel 'and invite all her close friends', Joey just has to yell to Ross in the bathroom...and they're all invited.
Another episode has Chandler, making up an excuse to leave, say he's going to meet up with some friends. When he's gone, a confused Joey asks, "He has other friends?"
Whenever the friends do try to become friends with other people, it usually never lasts because the friends or the new friends don't like each other. An example of this is when Joey gets a female roommate and leaves after a few episodes because she couldn't stand Monica and Chandler and Joey refused to ditch them.
Plus the writers ensure no Love Interest sticks around long enough to work their way in. Two thirds of the gang pair off, (Chandler/Monica, who are together for 6 seasons and Ross/Rachel who have an on/off relationship for the whole show) and Joey's still single by the end. Phoebe is the only one who actually marries outside of the group, and even then her boyfriend didn't become serious until the last season and their wedding was a couple of episodes before the season finale.
And ironically there are always a lot of people (in the background) at their parties. A bit strange since the friends don't seem to hang out with anyone but each other.
George: It would be good if he [an employer] saw me with some of my black friends. Jerry: Except you don't have any black friends. And outside of me, Kramer, and Elaine, you don't have any white friends either.
Kramer occasionally makes reference to other friends of his. When Jerry asks why they've never met these friends, Kramer shoots back that his other friends wonder why they have never met Jerry.
In fact Kramer, of all of them, is clearly the one with the biggest visible social circle - Newman is clearly a close friend and less frequently we also see his pal Mickey.
Don't forget Bob Sacamano.
It's debatable whether or not even the four main characters on Seinfeld could really be considered "friends." They generally just use each other as pawns in their own hairbrained schemes. Rarely do they sincerely help or show any real compassion for each other.
Degrassi The Next Generation has a cross-clique cast. Up until Season 4 there were only two grades of importance. Since then there was always one empty grade, which lacked any sort of main cast to it. However the cast can be friends with just about anyone in the opening titles, or at least aware of their lives. Which is odd given the size of the school.
On Psych, none of the characters are exactly social butterflies. It becomes more explicit in one episode when Shawn and Juliet leave town briefly. Gus, Lassiter, and Henry are left sitting around and catching up on grocery shopping. They even all bump into each other while shopping and have a conversation that amounts to "We're busy this weekend, right guys? We totally have friends who aren't Shawn or Juliet!"
Buffy the Vampire Slayer is another example of this trope. It was partly explained away in-show in the early seasons by many plots turning on the fact that Buffy and her friends were unpopular and socially ostracized by their fellow high school students. After the gang graduated from high school, the show did a Story Arc based on the supposed dissolution of the gang, only to inevitably bring them all back together having learnt An Aesop about the value of their friendship.
In fact, after the "Core Four" characters (Buffy, Xander, Willow, and Giles) were established in the first episode, any new cast members were almost invariably love interests of the original characters. The only exceptions were Dawn (we'll just say she was adopted and leave it at that) and Spike (at first) because a super-strong vampire ally is too useful to turn down.
In addition, almost all of the love interests were inevitably connected to the supernatural in some way, or at least more strongly aware of Sunnydale's proclivity for vampires. Inviting true Muggles into their business usually ends badly.
Lampshaded in one episode where Buffy invites Sophie, a friend from work, to her birthday party.
Buffy: What? Like I'm one of those losers who can't make friends outside her tight little circle? No. I'm friendly. We bonded instantly. Peas in a pod. Bonded peas.
Anya: Really? Um, what's Sophie's last name?
Buffy:(pause) Okay, shut up.
Lampshaded again in "Flooded". When someone calls Buffy at the house, she wonders aloud, "Who's calling me? Everyone I know lives here."
LazyTown's nine recurring characters appear to be its entire population, despite the grocery store and bank that are occasionally visible in the background, and the houses that clearly don't belong to the cast visible in aerial shots of the town. When you add in the invisible parents of the child characters, the effect is rather creepy if you give it too much thought.
Not to mention the fact that the mayor also doubles as the town's librarian, school principal, postmaster, banker, shopkeeper, etc. Presumably because the rest of the town's citizens are too lazy to do their jobs.
Sportacus also seems be the only form of law enforcement in the town, though the only people who ever seem to get into trouble are the other eight main characters.
Somewhat justified in How I Met Your Mother: Robin's from Canada and only recently moved to New York at the start of the series and, because he threw away his life before 2001, the only people that Barney knows other that the girls he sleeps with are his work buddies. We know Marshall has law buddies, but, except for Brad in a couple of episodes, we don't see them regularly enough. However, we rarely see one of Lily or Ted's friends outside the circle, and we aren't really given a reason why.
We've seen one of Lily's friends. When they're together they revert to the way they acted when they were closest.
Lily's other friends, other school teachers, turn out to be Whoo girls who have more in common with Robin.
In the same episode as the above example, we also meet Ted's friend Punchy (Adam Puncherelli), who has appeared other times, such as when Ted is almost his best man.
Lampshaded in one episode where the gang is stranded in Barney's apartment during Hurricane Irene. Ted says he has something to say, and he means it from the bottom of his heart: He wishes he had branched out and made more friends in his twenties.
S Club, though being an English band that moved to the US (and to Spain for the last series), who change cities every few weeks, it mostly makes sense.
Coupling. In the first episode the two main characters have their partner (the other main character), one close friend, and their ex. The two circles combine, giving them each another friend. (When Jeff gets replaced by Oliver, he brings in his ex, but it's still a very small circle.) It's particularly strange in Susan's case because, while Steve and Patrick become good friends, Susan doesn't even like Jane but they hang together a lot.
The four main male characters of The Big Bang Theory seem to both hang out together and work together (at separate departments in Caltech). But there are occasional glimpses into an expanded social circle, just not one we see on a regular basis like Stuart from the comic book store. Because of the way the show is set up, it often seems like they have more friends than the supposedly cooler Penny, whose friends seem to mainly consist of 24 Hour Party People.
Penny has been shown at times to have many friends outside of the main cast, we just very rarely see them or get a name because they are part of a group. It's implied she knows how awkward they can be in social situations and avoids introducing them (not even her geek boyfriend, especially when watching football). In later seasons Penny social circle really DOES seem to have dwindled down to just the guys, Amy, and Bernadette but it can probably be explained away as Leonard destroying her "ability to tolerate idiots" extending past just the people she dates.
Sheldon explicitly limited his friends cap to four people, because he doesn't care to waste energy on five or more. He also is the most averse to new social experiences, often ranting at newcomers like Priya, Bernadette and Stuart for upsetting his own personal status quo. Typically after a few episodes he ends up warming up to them but he is the poster child for "socially awkward genius."
Howard's bachelor party reflected an aversion of this trope; in addition to the core group of himself, Raj, Leonard, and Sheldon, the party was also attended by Stuart, Barry, and Wil Wheaton, who were making their 15th, 8th, and 5th appearances on the series respectively.
Frasier has references made to Daphne's friends a few times, and even a small number of appearances or telephone conversations for them. And while Martin has his bar friends and old buddies on the force, we only hear of Roz's dates, not her friends. Frasier and Niles' close relationship is even used as a plot point, with Frasier realising that Niles is one of his very few friends. He even laments at one point that he had a larger circle of friends when he was in Boston.
This gets used as the impetus for the plot of one episode, where Frasier decides to try and use his radio show to make new friends. The one guy he does arrange to meet, however, turns out to be a total bore who only talks about esoteric things that he personally is interested in.
Justified for most of the main cast in Pushing Daisies - Ned has long been fairly aloof, Emerson is grumpy and Chuck spent most of her life taking care of shut-ins, but it seems weird that Olive doesn't appear to have any other friends. Admittedly, her personality might be a little bit much for some, but you'd think there'd be plenty of others who'd find her charming.
Well, she seems to be in reasonably good terms with her old jockey pals.
The Power Rangers, especially in the original series, never seem to hang out with anyone except each other, and especially in the early seasons never seem to even talk to any civilians on a regular basis aside from Ernie the juice bar guy and Bulk and Skull. Anyone else they crossed paths with would be a one-off character who they would rescue from the bad guys and then never see again.
This was especially ridiculous because the Rangers as originally written were supposedly some of the coolest kids in school (even Billy, somehow) yet they didn't seem to have any friends outside of their Five-Man Band. And if they did make a new friend, he or she would end up becoming a Ranger before long.
Similarly, the Dino Thunder Rangers seemed to spend a lot of time together despite the fact that they explicitly came from different social circles before becoming Rangers: Conner's a jock, Ethan's a nerd, and Kira's a rock musician - local Alpha Bitch Cassidy even wondered out loud why the three were even talking to each other when she first saw them. It helped that Ethan introduced the others to the Local Hangout and they started frequenting it too, but still...
Thus was finally justified in Power Rangers Samurai, where an episode was devoted to the Green Ranger trying to hang out with non-Ranger friends, only to learn that it wasn't safe for them, with the decision (reinforced by advice from the mentor) to avoid non-Ranger social contact until the fighting is over. A later episode also addressed the Blue Ranger's social circle, as he ran into his old swim team who were still a little bitter over how he suddenly abandoned them (for Ranger duties, though they didn't know that).
During the first two seasons of Gossip Girl the characters all seemed to have large social circles (except for Dan, but you don't get the nickname Lonely Boy for nothing). In season three the social circles for the members of the Non-Judging Breakfast Club seem to have shrunk down to just the four of them (well, Nate also hangs out with Dan, but that still makes it a limited circle). In the later half of the season this is lampshaded when Blair heads off for a fashion show where she has "thirty friends attending", causing Nate to turn to Serena and ask: "What, what friends?"
iCarly has a Power Trio of Sam, Freddie and Carly. You can stretch that circle to include Spencer, and maybe Gibby.
On Victorious, if a student in an episode besides Tori, Cat, Jade, Andre, Beck or Robbie (and occasionally Trina or Sinjin) has a major part, it's a safe bet you ain't gonna be seeing that student again.
Done to the extreme on The X-Files; the social circle consists pretty much of Mulder and Scully. Gravitating around them are the Lone Gunmen and Skinner. And that's pretty much it. Scully is seen initially to have at least one friend outside of her work, but she is never seen after that episode. Mulder is a loner by nature. This makes sense, though. With their 24/7 jobs, the danger that surrounds them, and the implausibility of their work, what friend outside the tight social group would believe them or stick around?
Taken to an equal extreme on In Plain Sight, when Marshall and Mary's social circles consist of . . . Marshall and Mary. Over the years, the rises and falls a little bit. Raph and Bobby D join and leave. Abigail hovers at the edges. Stan joins and seems to stick. Even lampshaded by Brandi, who's frantic that she has no guests to invite to her wedding.
Brandi: Who are you bringing?
Mary: Marshall. I don't know, Stan, maybe?
Brandi: WE'RE LIKE THE FAMILY WITH NO FRIENDS!!
On Leverage, the crew seems to entirely make up the character's social circles. Explicitly discussed in one episode. Apparently, outside the True Companions Elliot has some old military buddies, Hardison has some online friends, Sophie has a fellow grifter or two, Parker is experimenting with "normal person stuff" with her sole friend, and Nate . . . well, Nate has his ex-wife. So, at max, two or three non-True Companions friends total.
Boy Meets World had Heterosexual Life-Partners Cory and Shawn and Cory's girlfriend Topanga. The later seasons saw the expansion of the social circle when Angela, Jack, and Rachel were added, and Eric went from just being Cory brother to being part of their social circle.
Red Dwarf was deliberately this for most series, with Lister, Rimmer, The Cat and Kryten (as well as Holly the computer and later Kochanski) being the only characters for most episodes. In Series 8 however, the ship and its crew have been resurrected, but none of them hang out with the original crew. This is justifiable in that they're in prison, and Lister's old friends aren't. Sadly, he never gets to meet them in the series due to the fact the original actors weren't available.
The study group of Community are extremely reluctant to let anyone else into their group. Membership of the group is Serious Business, as can be seen in Buddy and Chang's attempts to get in and the group's eventual decision to cast Pearce out. Other students at Greendale have come to grow weary of how everything always ends up being about them.
Played ridiculously straight on Saved by the Bell. Not only do we rarely see the six main characters interact with other Bayside High students, but they also appear to be the only students in the school that actually do anything. In other words, pretty much every other student on the show is just a Living Prop.
Freaks and Geeks is a rare example of this trope being played in a realistic manner. Both the Freaks and the Geeks are very close-knit but also regularly interact and have casual friendships with other Mc Kinley High students (the most prominent examples being Harris Trinsky and, in the later episodes, Gordon Crisp).
Inspector Tommy Lynley and his partner Sergeant Barbara Havers do spend time with people other than each other, but none of them seem to last more than a few episodesnote Christine Wood, Lynley's Love Interest in series 5, whom he winds up ditching for Barbara, or at most a single seriesnote Azhar and Haddiyah, Barbara's sort-of Love Interest and his daughter, in series 2, who regrettably vanish after that series' finale. The only characters to not fall victim to this, aside from their police superiors, are Lynley's wife Helennote who is Killed Off for Real at the end of series 5, and their reconciliation likely wouldn't have lasted anyway, their coworker DC Winston Nkatanote who first shows up in series 5, and the Medical Examiner Stuart Laffertynote ditto. And even they aren't seen hanging out with the main duo outside of work to any great extent. And finally, they can't be apart for any great length of time. Lynley goes to Cornwall for vacation? Havers goes along. Havers gets demoted? Lynley calls her in on every case he can. Let's face it; at the end of the day, they just keep coming back to each other.
The original Battlestar Galactica mainly consists of Apollo, Starbuck and Boomer. All three of them are warriors who don't take too kindly to either the Council of the Twelve or the 'Blackshirts'. Sheba is later added to the group sometime after the Pegasus disappeared.
The playable cast of Persona 4 only seem to hang around with each other, sans whoever you make the PC interact with. At one point Yosuke does invite Kou and Daisuke to hang out, implying they're on good terms, but none of the other cast members mention friends outside of the Investigation Team.
In Misfile Ash and Emily's social circle is basically each other and one drunken angel. It's expanded slightly since it was lampshaded in this comic but not by much.
Justified. They're both so disoriented from the misfile that they basically lose track of their other friends. Ash can't stand facing people she used to know now that she's a girl, and Emily is pretty devastated by losing two years, so hanging out with her friends (who are getting accepted to college) is too painful.
John, Rose, Dave and Jade in Homestuck, with the added oddity that they're Internet friends living in Washington state, New York state, Texas and a Pacific island respectively. None of them seem to have any real life friends at all.
Ironically, this trope still applies even though the webcomic has an astonishing Geodesic Cast.
The alpha kids have a similarly small social circle, though at least on Dirk's and Roxy's side it's justified by the fact that Jane and Jake are apparently the only people Calliope's software allows them to contact. This is lampshaded at one point by Dirk, when he points out (regarding the love triangle between himself, Jane and Jake) that given how few people they all know — and taking their respective orientations into account — Jake was pretty much the only romantic option either he or Jane had.
Neurotically Yours has an extremely limited social circle. Germane claims to have friends but the only people she was ever seen with was her temporary roommate and the creepy pizza guy stalker. Likewise, Foamy the squirrel claims to have a ton of followers but he is only seen hanging out with Germane and two other squirrels named Begley and Pillz-E.
Jimmy Neutron never really hung out with anyone beyond his group of four friends. It was lampshaded at least once when Carl and Sheen engaged in an Ultralord argument during one adventure, leaving Jimmy to grumble about needing to expand his circle of friends.
In Ed, Edd n Eddy there are only 12 characters in the series, Ed, Edd, Eddy, the Kanker Sisters, Kevin, Nazz, Rolf, Johnny, Jimmy, and Sarah, and Plank if you can call a piece of wood a character. In fact, this was lampshaded in the later seasons, when they go to school and there are no visible teachers or other students. They sometimes mention their parents but they are never seen.
Kim Possible and her sidekick Ron are close friends since pre-school, but outside of each other they only have one close friend each (Monique for Kim, Felix for Ron) both of whom they meet during the series. Ron is established to be something at the bottom of the school "food chain", but Kim is established as quite friendly with everybody. However, despite being a cheerleader and A grade student, most of her interactions with the rest of the school are very much in the tone of an isolated leader (as captain of the cheer squad, and a thousand other commitments), as her continuously saving the world leaves her little time for the rest.
The Magical Girls in W.I.T.C.H. are close friends — scarily close. There's only one other girl who they so much as talk to in the average episode, and she turns out to have powers too. They did some good Lampshade Hanging about it; in the second episode, Taranee notes that being a new girl in their circle is very uncomfortable, and they get into serious trouble because they never invite anybody else to join them for fun (except the 24 Hour Party People).
Possibly justified as they have little time for socialization due their fight for Kandrakar (and its tendence to butt in what social life they still have). Also, Will suffers from trust issues (the reason being evident to anyone who read the comics), and is somewhat of a miracle that she has a social circle.
In Danny Phantom, Danny, Tucker, and Sam only hang around with each other. The three are unpopular "losers" in their high school, but they rarely seem to interact with other Goths and Nerds and whatnot. The only person who joined their niche circle permanently was Jazz (though Sam was most vocal against her joining the group) and she's Danny's older sister and she only appeared if plot called her for it.
The main characters in South Park actually became this over the years. In the beginning of the series, they would frequently interact and play with other kids in the schoolyard. Over the years however, their Weirdness Magnet has slowly pushed people away. One episode explicitly states that the rest of the kids don't really care for them.
Craig: No. That never occurred to you. Because you guys are jerks, and you never learn from your mistakes, and that's why everyone at school thinks you guys are assholes.
Kyle: That's not true. Kids at school like us. Don't they?
Stan: Yeah, dude, kids at school totally like us. Craig is just being a dick because we're having a tough time right now.
Craig: I'm being a dick?
Craig: You guys took my birthday money, got me arrested and sent to Miami with no way home except to take down the country of Peru, and I'm being a dick?
Cartman: There's no talking to this guy.
KaBlam!!: We never see any of Henry and June's other friends. They're never mentioned, either.
Same with Life with Loopy. While we have seen Larry's friends in one episode (the last episode aired, actually), we never see Loopy's school friends. However, we were, gonna meet them, if season five, you know, aired.
Phineas and Ferb: Candace is only seen hanging out with three other teens: Jeremy, Stacy, and Jenny. So pretty much one can say she doesn't have that big of a circle. It's even lampshaded in an episode when Candace is looking over her contacts list for friends and the only people there are the three listed above, and her mom. Also Buford, whose presence in her list is something she cannot understand, but she soon deleted him.
Totally Spies!: The only person Sam, Clover, and Alex regularly interact with at their school (outside the 3 of them), is Mandy. Any other classmate they were seen talking to would be gone by the next episode, never to be seen or mentioned again (except for maybe the occasional boyfriend that would last about 2 or 3 episodes). Possibly justified in that their lives as spies would realistically get in the way of them having normal social lives.
Doug actually subverts this trope to the opposite extreme: Just about everybody in the entire sixth grade is friends with one another (even Roger, the class bully, is usually invited to pool parties, dinners, etc.). And, apparently, the students at the Bluffington School are the only grade school students in the entire town.
Family Guy has the Griffin family be only friends with a few neighbors and their families, namely Joe, Quagmire, and Cleveland before he moved away. The first few episodes in season 1 showed Peter hanging out with a bunch of other men for drinking but they were quickly written off in favor of a more focused friendship Peter has now.
Brian: Aw, look at that. There's the old gang we've gotten to know so well over the years.
Thomas the Tank Engine though originally a very expansive universe, began to streamline the cast following Hit Entertainment's takeover, introducing the "Steam Team" dynamic that consisted of eight main engines who had main focus for most episodes, aside from occasional new characters getting introductory stories. This became even more limited as the majority of episodes became Thomas-centric only, though this has started to get downplayed.
The Planet Express crew in Futurama never seem to hang out with anyone except their coworkers - in later seasons, the office seems to be used more for hanging out than for any actual work. Most of them (particularly Amy) are implied to have active social lives, but only the occasional short-lived romance is ever shown on-screen.