A series has a segment focused on an increased threat to order and/or safety in the setting.
Shining Armor: A threat has been made against Canterlot. We don't know who's responsible for it...Chekhov's Gun, and talk of it as a Chekhov's Lecture, relating to conflicts later on... except when things cool off before getting worse, in which case the implied theme is often that characters were over-reacting to such concerns. This is often presented in a context that shows its timing coinciding with some other major event. (Ie. Celebration or sporting event happening around the same time as such threats to stability; not unlike how that is often the case in real life.)
- My Little Pony: Friendship Is Magic: The two-parters in general are this in comparison to the rest of the series, catching most major characters off guard in each case. The rest of the series' conflicts seem mundane in comparison.
- The Canterlot Wedding two-parter involved a wedding plan coinciding with a need for increased security due to a mysterious threat against Canterlot. (Turned out it was connected to the wedding, namely due to the involvement of Chrysalis and the changelings in each.)
- The Nightmare Moon arc involved the threat of eternal darkness.
- The Discord arc involved the threat of chaos.
- The King Sombra arc involved the threat of the enslavement of an entire kingdom.
- Seven Days was an entire series about this trope, in which The World Is Always Doomed but a lone time-traveler has the chance to investigate and circumvent such disasters.
- In the Star Trek: The Next Generation episode "Force of Nature", warp drive (which powers all Federation starships) was found to be damaging to the fabric of subspace. At the end of the episode, the Federation decided that until they can figure out a way to counteract the rifts in space, all ships can't go above Warp 5 except in emergencies.
- South Park parodies this trope with their Cartoon Wars two-parter; in the first episode, Family Guy resorts to shock value by doing a caricature of Muhammad, and after some Islamic fanatics make vague threats of revenge, the residents of South Park are afraid that they will be targeted by terror attacks. In the second episode, the revenge turns out to be a cartoon of caricatures of various aspects American culture crapping on each other.
- The Star Wars prequel trilogy provides an interesting variation on this; the galaxy was under imperial control in the original trilogy, but the prequel trilogy focuses on explaining the instability that led to such imperial control. Due to the nature of the storyline, however, the feel of a society-on-edge episode still comes through.
- The last season of Battlestar Galactica (new series) focused much more than previous seasons on the deteriorating conditions in the rag tag fleet (this being a post-apocalyptic society to begin with)
- The opening episode of Season Two Veronica Mars largely features the town losing their shit after a long string of privileged rich people get away with crimes they obviously committed. Later on, Veronica and Logan (one of the aforementioned rich people) narrowly dodge a drive-by shooting--violence which the series typically avoided until the first season's finale.
- Also the last episode of the Live Action TV cyberpunk miniseries Wild Palms ups the tension this way by showing society breaking apart at the seams as a result of the power struggle between the crypto-fascist Fathers and the more libertarian and humanistic Friends, secret societies that have been warring over America for decades.
- This is a recurring situation in Community. Greendale Community College is a sucky school and the students tend to get more volatile and over-the-top as finals approach. The major breakdowns occur once a year in-universe; which corresponds to one per season. In the past this has twice resulted in paintball competitions totally wrecking the school. In season three, the school loses most of its funding so things get even worse. An attempt to achieve a world record for the biggest blanket/pillow fort results in a civil war and a short time later the wake for a deceased student turns into a riot.
- Deus Ex: Human Revolution is set during a time when human augmentation (basically cybernetics) is starting to take off, leading to a divide betwen people who just want humanity to be "natural" and those who want to augment everything.
- The Dark Knight Rises involves a far more significant threat to Gotham than was presented by the villains of Batman Begins or The Dark Knight. Things also get dire much more quickly; the worst of the chaos in Batman Begins was resolved before most Gotham residents were even aware of it and the worst of that of The Dark Knight was fairly gradual due to the continuously worsening nature of the Joker's actions.
- While much of Babylon 5 involves political conflict and warfare, there's a particular segment of episodes in Season 3 before and including the station's secession from Earth where it becomes inevitable that station interests and Earth Government policy will irreconcileably clash, with the station itself coming into direct danger. Probably the range of episodes from "Voices of Authority" through "Severed Dreams" would fit the trope, although it could arguably start with Season 2's finale "The Fall of Night".
- And again in Season 4 after the events of Season 3's finale "Z'ha'dum", once we see the Vorlons bring out their planet-killers, with the Shadows following suit, destroying many inhabited planets ("The Summoning"), ending with "Into the Fire".
- And there's a third segment in Season 4, from "No Surrender, No Retreat" through "Endgame", when Babylon 5 and allied forces finally confront the Clark regime's forces and liberate Earth and her colonies.
- The Twilight Zone episode "The Monsters Are Due On Maple Street" concerns neighbors on a street who become paranoid when the power goes out and odd things start happening, putting the blame on aliens and then turning on one another due to suspicion.
- The Colour of Magic has this as an Establishing Character Moment for Ankh-Morporkians as a whole: a fire started in the rougher part of town soon spreads. Rich citizens are soon selflessly hacking down the bridges that span the river so the panicking crowds won't be able to invade.
- The Light Fantastic: a large part of the plot is caused by a very bright, malevolently red star appearing in the sky, and this drives the inhabitants of the Disc to start doomsday cults (Death himself finds them creepy).
- Psycho-Pass shows the Sibyl System controlled Dystopian Japan to be a society where most people don't think too much about how bad their society is, due to believing they are always safe since the Sibyl System can even monitor peoples' thoughts and "take care" of anyone who would commit a crime. Then comes Episode 14, in which a man kills a woman in front of numerous people in contrast to the other crimes shown up to this point in the series, which were hidden from the public. He is able to do this due to having a helmet which allows him to be undetected by the Sibyl System while wearing it. Although the criminal is caught, Episode 15 shows people discussing the crime, the internet is flooded with footage of the crime and people worrying that the Sibyl System does not protect them anymore. Worse, numerous criminals get helmets like the one in Episode 14, and riots begin. The citizens have to fight back against those with helmets to survive, ad soon violence and crime sweeps over the country that once had very few people ever worry about crime.
- Mobile Suit Gundam 00 in the first season had the episode "Trinity", where Team Trinity reflects on the chaos that had happened so far and how the world is disintegrating into varying stages of anarchy. Ironically, their arrival makes things worse.
- Stargate SG-1 has multiple episodes involving this. One example is season eight's "Full Alert," where the Goa'uld attempt to trigger World War III between Russia and the United States.
Hello, Unknown Troper. You'll need to get known to lend a hand here.