A Cool Loser Ordinary High-School Student is shown associating with a small, presumably tight knit circle of like-minded friends. But of course, the Call to Adventure arrives in all its glory, and our intrepid hero is plucked from normalcy and told that he's The Chosen One. Cool.
A couple training montages and plot twists later, the hero finds himself fighting against all odds and wanting for allies. Now would be a great time to call upon those friends that trust and like him enough to believe that the Statue of Liberty is actually a giant evil robot. Too bad those friends have ceased to exist within the plot. They are Social Circle Filler.
These characters are used to avoid presenting the protagonist as a friendless loner before falling victim to Conservation of Detail. Despite the appearance of close friendship with the protagonist, they promptly lose relevance after the hero is drawn into the Masquerade and introduced to new friends that aren't Locked Out of the Loop.
Contrast Friendless Background. Compare Forgotten Fallen Friend, where the death of a friend is used to set off the plot before being forgotten, and 24-Hour Party People, where hitherto-unseen "friends" appear to make a party seem more lively. Don't confuse with Those Two Guys, as they have a higher chance of coming back despite occasionally filling the same niche.
- A Place Further than the Universe utilizes the trope to heartbreaking effect with Megumi, Mari's friend who establishes her as a social person but quickly fades into the background as Mari prepares for the trip to Antarctica. Aware of her own growing irrelevance and that she's inadvertently built her identity on being a helper to the usually flaky Mari, Megumi spreads malicious rumors in an attempt to keep Mari home, but on the day of her departure confesses and acknowledges her failure. Mari rejects her attempt to end their friendship, and one of the first things she does upon returning at the end of the show is check on her, only to find that Megumi has successfully become the Hero of Another Story.
- Sailor Moon:
- Naru/Molly is Usagi's best friend until she meets Ami and Rei, then diminishes in relevancy to the point of showing up in all of one episode in the third and fourth seasons each, after more and more Senshi are introduced. Her manga incarnation fares even worse, as she doesn't even get the dignity of acknowledging the wedge between them and lacks a personal arc.
- An even better example are Yumiko and Kuri, two token female classmates who talk with Usagi for a few episodes until the actual main Supporting Cast is introduced — at least Naru showed up again. Not to mention the poor girl who never got a name — and due to being chubby is only known as 'Usagi's fat friend' by fans.
- In the anime it is difficult to take seriously the Senshi's comments on how lonely they are (without Usagi) when there are so many filler episodes dedicated to a senshi making friends with someone. But those friends never show up again...
- Psyren In the beginning, Ageha is seen with two friends in class, which he seems to be on good terms with. Once he gets roped in with Amamiya into the world of Psyren, we pretty much never see them again. Instead, Amamiya and Hiryu become his closest friends.
- Tokyo Mew Mew: Ichigo's friends Moe and Miwa appear in the first episode, and then once or twice afterwards, before vanishing completely.
- Averted in Ao no Flag. Though childhood friends Taichi and Touma reconnect in their final year of highschool while also befriending Futaba, the three still frequently hang out with their other circles of friends.
- Exaggerated in SSSS.GRIDMAN. Aside from Hass and Namiko, Rikka was friends with Toiko and Tonkawa among other members of the girls volleyball team. Akane's first Kaiju rampage pretty much kills everyone in her circle but the first two girls off, meaning everyone aside the Gridman Alliance essentially treats them like this in-universe and forgets about them the next day. Rikka herself Subverts this, as she continually keeps in touch with everyone who's still alive while keeping her forgotten friends' deaths in her memory.
- JoJo's Bizarre Adventure: Diamond is Unbreakable: Josuke is introduced with a trio of female classmates who are crushing on him. They are never seen or mentionned again, and Josuke is never portrayed a Chick Magnet again, since he's only shown hanging out with fellow Stand users Okuyasu and Koichi. This example is notable since Diamond is Unbreakable contains more slice of life moments compared to other Parts.
- In the early chapters of Death Note, Light Yagami hangs out with two unnamed friends who all but vanish afteward. Tellingly, the anime didn't include them.
- Robin Series: While some of Tim's school friends manage to avoid this (mostly just Ives and Zo, the rest disappear over time to never be seen or spoken of again) Kevin Hudman was hit so hard that later writers forgot about him so thoroughly that he was unknowingly merged with Hudson.
- Wonder Woman (1987): Later writers seemed to forget that Wonder Girl Cassie had friends outside of the superhero community, most notably her best friend, Secret Keeper and fellow androgynous tomboy George Redmond. First her last name was forgotten and then she never appeared or was spoken about again in any book despite Cassie appearing all over the DCU. Like Kevin mentioned above she was a Black and Nerdy teen friend of a teen hero from the '90s who disappeared without a trace, though in her case it likely happened because Cassie's personality was given a swift and shallow makeover in Teen Titans.
- Nova: Since Nova was initially modelled on Spider-Man, he had a supporting cast with friends such as "Caps" Cooper and Ginger Jaye, who appeared fairly frequently when he had his own title. Once he moved to the New Warriors, and later outer space, they disappeared, and Nova's close friends nowadays are generally shown to be fellow members of the New Warriors, or other cosmic heroes.
- 10 Things I Hate About You: Patrick is seen at the start of the film to hang around with a bald biker guy, who he smokes with and is his lab partner. As Patrick gets further involved with Kat, the character disappears altogether. When Patrick needs anyone to talk to later on, he goes to Cameron.
- Spider-Man: Mary Jane Watson is flanked by a Girl Posse for the first half of film one. However they quickly disappear and do not reappear for the rest of that film and despite seemingly being quite close, do not appear at her wedding for the second movie.
- Early in I Love You, Man we see Peter has several female co-workers who he seems to get on perfectly fine with; strangely, they are never mentioned again even though the plot revolves around Peter's lack of a close (male) friend to act as best man. The possibility of one of his female friends from work acting as his best man is never raised, even as an option to be rejected.
- Sam Witwicky has a best friend names Miles for the scene where he tries to go to a party, early in the first Transformers movie. The only other time we see him is when he blows Sam off when he calls to tell him his car is alive. Miles is then never seen or mentioned ever again.
- Terminator 2: Judgment Day: John Connors spends his introductory scene with a friend/partner-in-crime named Tim, who gives John someone to talk to before meeting the T-800 and reuniting with his mother, then never appears again.
- How I Met Your Mother: Robin in the very first episode is shown to laughing and joking with a few girls who are presumably her friends or co-workers. Once Ted is in her life and she joins the main cast, no mention of who they were is ever given.
- Buffy the Vampire Slayer: Cordelia's fellow cheerleaders or Oz's band.
- Actually averted in the first case. One of Cordelia's background "Cordettes", Harmony, appeared as part of the ensemble across three seasons, and became a recurring character in her own right and was given her own stories. The rest, however, play it painfully straight, as they were almost always different unnamed extras.
- Scrubs: Dr Cox is implied to actually have a circle of friends outside of the Hospital in season one. Shown in one episode, they are not used again and later episodes establish him as friendless and lonely.
- In Flash Gordon, Flash's Token Black Friend Nick appears in only 4 out of 21 episodes, one of them being the pilot.
- Glee : In the penultimate episode, "2009", we meet Bex and Lysander, whom we've never seen before, despite it being a Call-Back / Origins Episode to the Pilot.
- IZombie : Liv starts the series with a mother and a younger brother, but one might get the impression that she's a siblingless orphan.
- Sherlock: Mike Stamford is introduced at the start of the first episode as an old friend of John and one of the only people who can stand Sherlock for any length of time. He kicks off the plot by setting Sherlock and John up as flatmates, and is never seen again onscreen. However, he does receive occasional slight references in later episodes and is a frequent commentator on John's Character Blog.
- Kayla is this in the The House of Night series. She appears briefly in the beginning of Marked and briefly again near the end. After that she's pretty much forgotten in favour of the Five-Man Band.
- Justified in Brandon Mulls novel The Beyonders : A World Without Heroes, which starts off with a lot of interaction between main character Jason and his friends, the girl he likes, etc. They all become pretty irrelevant once he falls through into another world and discovers he has no way back, or even to send a message. His friends and families reaction to his disappearance is unknown, although Jason does think about it. Since Jason ends up back on Earth at the end, we'll have to see if the trope ends up being averted in the sequel.
- In Yume Miru Kusuri, Takeshi and Misaki are the main character Kohei's better friends. But once one of the three routes have been picked, they are completely forgotten.
- On Ruby's first day at Beacon Academy, her sister Yang encourages her to make friends of her own (so she doesn't have to hang out with Yang all the time) before Yang runs off with a nondescript group of friends. Said friends are never seen or mentioned again, as the titular team becomes Yang's main social circle.
- Later, during a slumber party for all the new students, Ruby writes a letter to her friends at her old school, who are also never brought up again.
- Batman Beyond: In the episode "Earth Mover," Dana is shown to be close friends with a girl named Jackie, close enough that both she and Terry spent the evening studying at her house and and hung out repeatedly over the course of the episode. Then Jackie promptly disappeared, not even getting any background appearances in episodes like "Revenant," "Eggbaby," or "Terry's Friend Dates a Robot" despite those episodes showing many school characters.
- My Little Pony: Friendship Is Magic: Early on, Apple Bloom was shown to be friends with a filly named Twist. Once the Cutie Mark Crusaders were formed, Twist was stuck as a background character, and Scootaloo and Sweetie Belle seem to be Apple Bloom's only friends. Enforced by real-life events: the character's voice actress, Alexandra Carter, left Vancouver for Philadelphia during production and became unavailable to record any further dialogue.
- Star vs. the Forces of Evil: Marco's friends Alonzo and Ferguson were written because the executives wanted Marco to have friends besides Star. They were seen in the pilot as well as earlier episodes in the series, but by the second season they're only mentioned once (in a joke pointing out their absence), and Marco's martial arts instructor basically takes over their role as "Marco's other friend(s)". They (and most of the show's Earth characters) are given a proper sendoff when Marco leaves for Mewni early in Season 3.
- This is a common issue with the biographies of historical figures and famous people. The world at large is mostly interested in the impressive things they have done, or the roles they have played in notable events, so superfluous details like friends or family are often downplayed or left out of the narratives entirely. This, in turn, can give a skewed picture of what the person was actually like and who/what they were interested in.
- Stalkers often have a psychological filter of this nature with regards to the objects of their interest. They tend to forget or edit out the fact that those they are obsessed with have people close to them, as this interrupts or ruins their fantasies.