When Hayate the Combat Butler does these with recurring minor characters, the fact is usually stated enthusiastically by said characters. Sometimes with the main characters complaining that they've been pushed to the sidelines. Of course, this is a given since the series has No Fourth Wall.
Shinkon Gattai Godannar!! has an episode dedicated entirely to the Bridge Bunnies and maintenance crew, mostly centering around the bustier female member of the maintenance crew as she got called for an arranged marriage that she later turns down.
Most of Pluto by Naoki Urasawa is told from the perspective of Gesicht, a one-shot character from the original Astro Boy series.
The One Piece anime has two episodes of "filler" based on the cover story arc of Koby and Helmeppo training to become great marines. Since this is canon (and plays important to the story later) it's hardly considered filler, and was a nice break from the previous chaos.
Mahou Sensei Negima!: During the Magical World arc, an important number of main characters are transported to it and the action takes place primarily there. There are, however, the occasional chapters that look back at the characters left behind in Japan and the UK.
The first Fullmetal Alchemist anime has an episode that focuses on Mustang's team. The episode is based on a number of omake from the manga, where Riza "disciplines" Black Hayate.
Batman Gotham Knight is an anime movie designed to bridge the gap between the films Batman Begins and The Dark Knight, made up of a series of vignettes by different animators. One of the vignettes shows a group of kids discussing/arguing about what they saw when they witnessed Batman fighting someone.
Episode 18 of Rental Magica featured mainly Daphne and Sekiren, showing what they were up to when Itsuki and Adilicia dealt with a demon problem the episode before.
Chapter 480 of Bleach which largely focuses on Ryuunosuke Yuki and Shino, two minor characters who were just introduced and barely had any plot relevance, other than being Afro-San's replacements.
Revolutionary Girl Utena utilized this for the second season during "The Black Rose Saga". Each of the Black Rose duelists were minor characters (save for Wakaba, who's a supporting character, and Kanae, who debuted in the arc) with ties to the Student Council members. The episodes were dedicated to watching them sink lower and lower into despair related to the Student Council, until they were easy prey for Souji Mikage.
One issue of Roberta Gregory's Naughty Bits focused on a week in the life of New Age co-worker Sylvia, while main character Midge (aka 'Bitchy Bitch') was on vacation. While her relentlessly positive attitude is a source of annoyance for the perpetually cranky Midge, here we see her as a much more three dimensional character who is just as much, if not more so, stressed out by her job as Midge is.
Several of Astro City series tend to focus on the viewpoint of minor characters in a Superhero universe, witnessing Crisis-level events from the sidelines or behind the scenes. The stories collected into a paperback under the title "Local Heroes" qualify best, focusing on characters such as a hotel usher and a lawyer working in Astro City.
Several Judge Dredd stories are told from the point of view of regular people with Dredd himself making only sporadic appearances in them.
IDW's Star Trek comic book usually re-tells the stories from the original series in the new timeline created in the 2009 Star Trek movie. Issue #13, however, is a Lower Deck Episode taking a very minor character from the film and giving his opinion of the main cast in the form of a letter home to Mom and Dad. It also reveals the fates of some of the original series Red Shirts in the alternate timeline.
The Homestuck fanfic "Outsiders" is about the meteor apocalypses upon two planets, as seen from the viewpoint of a completely mundane and unrelated bystander human and bystander troll.
The Harry Potter fanfiction The Ollivander Children looks at the Second War against Voldemort from the point of view of people who never meet Harry Potter and have no chance of fighting Voldemort, much less defeating him, and their particular struggles in the war.
After appearing as minor characters in several movies and a TV series, Jay and Silent Bob finally took center stage in Jay and Silent Bob Strike Back.
In response to the Bruce and Lloyd's unexpected break away popularity in the Get Smart movie, the spin-off movie Get Smart's Bruce And Lloyd: Out of Control was released, focusing on their escapades while everybody is distracted by Maxwell Smart's adventures.
Cloverfield is basically a lower deck version of every monster movie ever made. We don't see the perspective of scientists nor any important military figures. Because of this, we have little to no information about the monster and where it came from. Instead, the whole movie revolves around the nameless crowds of people who are trying to avoid getting squashed by the monster.
The 87th Precinct novel He Who Hesitates by Ed McBain is narrated by the criminal (and is the only one of the novels to have a first person narration) and the reader only gets to see the cops of the 87th Precinct as they appear to him.
The Warrior CatsExpanded Universe manga stories Ravenpaw's Path and Tigerstar and Sasha are this, focusing on minor characters amidst the clan wars.
The Dresden Files short stories Backup (starring Thomas Raith, whom we know to be Harry's half brother at that point), Even Hand (starring "Gentleman" John Marcone), and Aftermath (starring Karrin Murphy after the events of Changes). Except for a few moments in Backup, Harry doesn't even show up in these stories, focusing more on important people in his life dealing with the supernatural without him. In each story, the reader gets to see Harry through the eyes of his allies: in Backup, Thomas sees Harry as an artist and philosopher when it comes to magic, in Even Hand, Marcone reveals that all the anti-magic defenses in his stronghold are there in the event that he and Dresden go head to head, since Marcone sees him as a Worthy Opponent, and in Aftermath, Karrin has to deal with a supernatural investigation without Harry's help.
The War of the Worlds follows the first-person narrative of an Action Survivor, a simple middle-class scientific journalist. Likewise, the 2005 film centers around a dockworker who tries to survive the invasion with his two children. Apart from the opening and closing narration, we only know and see what's seen by him.
The Trope Namer from Star Trek: The Next Generation, as mentioned at the top. Specifically, the episode focuses on a group of four ensigns who are concerned about their performance evaluations, and figuring out which of them will have a chance to be promoted. Even when the focus shifts to the main cast, the discussion still involves the junior officers, since they're the ones running the evaluations.
The fifth-season Babylon 5 episode "A View from the Gallery" took the idea to its logical extreme by focusing on janitors on the space station, characters we'd never seen before and never saw again. The episode also hangs some lampshades. Ever try to figure out the purpose of those vaguely mop-like things are you see random crew members using in the background? So do they.
Bo: Well, what does it do? It's not a cleaner. Mack: I don't know. Maybe it strengthens the metal or something.
The 5th season episode "Proving Ground", about some previously unseen cadets in a Stargate training program (one of them had appeared in the 4th season episode "Prodigy", but three were genuinely new).
The appropriately-titled 6th season episode "The Other Guys", which was also a subversion of All Up To You.
The 7th season's "Avenger 2.0" featured the same characters from "The Other Guys".
The 8th season's "Citizen Joe", in which a mild-mannered barber gets psychic images of the SG-1 team and tells the stories to his wife and friends — thus also allowing for a Clip Show.
The revived series has such an episode in series 2 and 3 doubling as Bottle Episodes. Usually called "Doctor-lite" episodes in the fandom, these two, titled "Love & Monsters" and "Blink" focus on Muggles with only peripheral access to the Doctor's world, and how those characters react to High Weirdness without the Doctor around to explain what's going on. "Love & Monsters" notably had point of view shots of the central character referring to other episodes.
The 2005 Christmas special "The Christmas Invasion" has the newly-regenerated Tenth Doctor unconscious until near the end, with most of the action up until then focused on UNIT and the prime minister.
From the classic series, there is "Mission to the Unknown", which doesn't feature any of the regulars at all, but leads into "The Daleks' Master Plan".
The Torchwood episode "Random Shoes". It was actually narrated by the protagonist of the episode to differentiate it even further from the normal episodes.
Highlander had the episode, "They Also Serve" which focused on Joe Dawson and the other Watchers.
The series of episodes starting with "Bop Gun" and ending with "Blood Wedding" which showed Murder Investigations from the perspective of those left behind.
The final third-season episode, "The Gas Man," follows two new characters as they stalk main character Frank Pembleton and his wife around Baltimore. A variation on this trope, as it wasn't done to free up the main cast for other episodes, but as a screw-you to NBC for the show's constant near-cancellation.
The Battlestar Galactica (Reimagined) has many a Lower Deck episode, often coupled with a Day in the Limelight. Episodes focus on the literal lower deck with Chief Tyrol experiencing the troubles the of fuel shortages and labor disputes. There are also Day in the Limelight episodes focusing on less important pilots. The movie, Razor, is almost an entire Lower Deck/ Limelight of The Pegasus, its former Captains, and its XO.
The lighthearted Breather Episode slash Bottle Episode "You Kill Me," about The Lab Rat Hodges (not himself part of this trope, being a credits-listed character by this point) running the other Lab Rats through elaborate (and absurd) murder scenarios as part of a CSI-themed board game he was creating. The previous episode featured the Put on a Bus departure of a main character, while the following episode concerned another main character breaking down after becoming addicted to prescription drugs.
Another episode titled "Lab Rats" features said lab rats trying their best to solve the season's Myth Arc. They didn't do a bad job either, actually identifying a fairly important clue about the killer's psychosis.
Desperate Housewives season five featured a look back at the life of a previously seen character, handy-man Eli Scrugs (played by Beau Bridges), with the main characters remembering their most significant encounters with him, ending with a flash-back to Scrugs himself visiting Mary-Alice just before her suicide, which opened the series pilot.
The episode "Good Shepherd" was a Lower Deck Episode that literally showed the lower decks — the dimly-lit, poorly-maintained areas where the real work of keeping a poorly-supplied refugee ship running was carried out. The three redshirts focused on were misfits who under normal conditions would have been transferred off Voyager long ago, were it not for the long walk home. (They don't get sole focus, though, sharing the episode with Janeway. On the other hand, their interactions with Janeway - and each other - make up the majority of the action, and their character development.)
"Learning Curve" was a similar episode, which focused on training Maquis crewmembers that, unlike Chakotay or Torres, had no Starfleet experience whatsoever. Tuvok plays as close to Drill Sergeant Nasty as a Vulcan can get.
Season 8 has "Their Story II", focused on and narrated by the interns that have been slowly introduced since the beginning of the season. As a result, it's remarkably similar to a season 1 episode.
The episode that followed "Their Story II", "My Full Moon", featured none of the main cast except for Elliott and Turk. They discuss their fears during a night shift while watching over the interns, who collectively get an equal amount of screentime as the two regular characters.
Remember WENN had an episode where Victor and all the actors disappear after the first few minutes (off to a convention in Harrisburg) and as a result Betty and and the minor station employees have to keep the programming going for a full day.
Double subverted in the Sanctuary episode "Icebreaker". The episode opens with Henry (a supporting lead character), Declan (a recurring minor character), and a bunch of newbies on an isolated ship in the Bering Sea. The audience expects this trope when the characters reveal that Magnus and Will (the leads) are on their way but severely delayed by the heavy storm, but the trope is subverted almost immediately when Will and Magnus arrive. Double subverted when the real Magnus and Will show up at the end of the episode and reveal that the earlier pair were shapeshifting abnormals.
The Sopranos began its third season by having a particularly unremarkable day for the titular family shown through the eyes of the rarely-seen FBI. Overlaps with Villain Episode.
Played with in a 30 Rock episode shown as an episode of "Queen of Jordan". Angie's effort to organize a charity fashion show keeps getting overshadowed by the show's focus on Jack's Unresolved Sexual Tension with his mother-in-law, Liz's feud with a baby and even Kenneth's feud with a power cord. Technically, it's a lower deck episode of her show.
An interesting example in the Person of Interest episode "Relevance". The premise of the show is that a secret government surveillance supercomputer can predict acts of terrorism and, as a by-product, spot ordinary civilians who will be involved with violent crimes. The protagonists are the ones who deal with the latter, the so-called "irrelevant" list, so its jarring when an episode late in the second season suddenly focuses on Shaw, a Bad Ass assassin whose job is to follow up on the "relevant" list. Much like the Doctor Who examples, their paths cross briefly but we follow Shaw for the whole episode and the protagonists appear in a barely a handful of scenes.
A lower deck scene occurs in 1776 after "Cool, Cool, Considerate Men" when custodian McNair, his assistant, and the Courier are left alone. They joke about how noisy, aristocratic, and eager to start wars without fighting themselves Congress is. Then the Courier sings "Momma, Look Sharp" when asked about the fighting.
Half-Life: Opposing Force and Half-Life: Blue Shift follow the events of the first Half-Life from the point of marine Adrian Shepard (one of the troops sent to clean up the mess in Black Mesa by shooting who knew about it, thus one of the bad guys in the base game) and security guard Barney Calhoun (a Black Mesa security guard and friend of the protagonist) respectively. While Barney went on to a supporting role in Half-Life 2, fans are still waiting to find out what happened to Shepard.
Halo 3: ODST begins roughly halfway through Halo 2 and ends with the beginning of Halo 3. It follows the story of a group of ODSTs trying to fight their way through the ravaged city of New Mombasa. (Which was ravaged back in Halo 2, though the player didn't get to see much more than that.)
Resident Evil 5 has two DLC of these, "Lost in Nightmares" the prequel to the game, and "Desperate Escape" shows Jill and Josh escaping the Tricell facility, taking place while Chris and Sheva fight Wesker.
Resident Evil: Revelations, has a couple of short chapters where you control minor characters Quint Cetcham and Keith Lumley. Unlike the major characters, their mission are meant to be mostly comedy relief that play on the Buddy Picture tropes.
Medal of Honor: Underground focuses on Manon Batiste, the player's advisor from the first game, before and during the events of that story.
FEAR 2: Project Origin involves an SFOD-D squad near the end of the first game. The expansion pack's protagonist is a Replica redshirt who gets possessed by Fettel.
Syphon Filter: The Omega Strain casts the player as an IPCA rookie codenamed Cobra, although Logan and the other main characters are playable in the bonus missions.
Dead Space Extraction features, for a short time, Karen Howell, a botanist, who worked in hydroponics. She kills a brute protecting Lexine, but she dies when she calls Warren out for seeding Unitologists into every corner of the ship. Immediately afterwards she is attacked by a tentacle and left to die by Warren while he yells about his "god" having different plans. This leaves the player in serious doubt of his character.
Round 6 of Fite! leaves Lucco and Guz, the main characters thus far, to focus on Ricci, who had only appeared briefly before then.
One chapter of GastroPhobia is focused primarily on the Cuckoos and Lord Nightsorrow. It's called "Not Everything's About Phobia".
Act 5 Act 1 of Homestuck, aka Hivebent, focused entirely on the trolls, who had previously been secondary characters only known by their screennames, while doubling the main cast. Some of those trolls remained side characters, while others...did not.
Any LoadingReadyRun video featuring Kathleen and her kooky friends is one of these since they deviates from the usual cast and location so drastically. (Includes "Job Hunt" and "Stuck In A Car With Your Friends".) They're usually made due to filming constraints. Namely, the fact that Graham's in Prince George at the time.
"Isabella and the Temple of Sap" is a Lower Deck version of "Bubble Boys," showing Isabella's Fireside Girls troop getting the sap needed for her crush's project at an abandoned amusement park. The sub-plot even has some fun with this by featuring her dog Pinky on a secret agent mission rather than Perry (who does make a little cameo).
"Not Phineas and Ferb" centers around Irving trying to convince his brother that Baljeet and Buford are Phineas and Ferb. The only things Phineas and Ferb do in the episode are watch a movie and show up in the backyard just in time to make Candace look insane.
"Deliver of Destiny" shows a day in the life of a delivery truck driver named Paul who gets caught up in the wacky hijinks of both Phineas and Ferb and Perry the Platypus.
BURN-E shows what BURN-E was doing while WALL•E had his adventures on the Axiom.
Similarly, Jack-Jack Attack shows what was happening with baby Jack-Jack and babysitter Kari while the rest of the Parr family was off playing superheroes. This was intended to be part of the movie, but was cut for pacing reasons.
George and AJ is about the two retirement home workers sent to get Carl Fredericksen from Up, who witness firsthand Carl's unintentional starting of a trend of old people escaping from retirement home life by turning their houses into modes of transportation, most of which are even weirder than Carl's.
Star Wars: The Clone Wars had "Rookies", a clone-focused episode with the main characters as supporting characters. Its predecessor, Star Wars: Clone Wars managed to have episodes entirely without Jedi, but that's only because the episodes were 3 minutes long.
"A Million Little Fibers", in which pot-smoking sentient towel Towelie runs afoul of Oprah Winfrey's talking genitalia.
"Butters's Very Own Episode" focuses on Butters, a minor recurring character up to that point. This is an interesting case in that, after that episode, Butters became a much more prominent figure; these days, he gets more screen time than anyone aside from the main four (and way more lines than Kenny). It is also notable for coming out of completely nowhere; it was the last episode of a season, and the preceding episode ended on a massive cliffhanger.
Referred to in another episode focusing around Jimmy, where Stan says that the plot looks like one of those misadventures that spiral out of control, and that they should just keep out of it. We don't see the regulars again until the end of the episode where Stan shows relief that they stayed out of it.
A second season episode of Gargoyles features Vinnie, a disgruntled ex-Faceless Goon who blames the gargoyles for his unemployment. While plotting his revenge, he narrates clips of his prior encounters with the gargoyles, interjecting his own POV.
"The Invisible Hand of Fate," a third season episode of , primarily centers around Billy Quizboy. The series subverts this by making the lower deck episode extremely important to the overall plot. The ep gives us backstory info for nearly every major character, and reveals how Brock became Dr. Venture's bodyguard.
Billy gets a second episode ("The Silent Partners") in season four. It's also highly plot-relevant (it sets up the season finale.)
Any episode of My Little Pony: Friendship Is Magic starring the Cutie Mark Crusaders is pretty much this. One episode, "Hearts and Hooves", doesn't have ANY main characters except for a small speaking cameo from Twilight Sparkle. "Family Appreciation Day" is focused on Applebloom and none of the Mane Six other than Applejack appear.
"The Greatest Story Never Told" focuses on Booster Gold, who gets tasked to the sidelines while all of the greatest heroes are fighting a frighteningly powerful menace, and what he accomplishes in the background while no one notices.
A sequence of Aqua Teen Hunger Force episodes centers on Carl and the Aqua Teens' landlord Markula. The Aqua Teens themselves are absent, having been cocooned by military spiders in the Mojave Desert.
The episode "The Big Scoop" in The Fairly Oddparents, third season, was Chester and AJ's version of what happened in "A Wish Too Far." When they notice Timmy's sudden popularity, at the same time required to write for the school newspaper, they investigate to find out how he got popular. The voices were redubbed due to different voice actors for Chester and AJ, and the animation was also changed, possibly to match the pace of the dubbed version.
The framing device for the Recess direct-to-video special, "Recess Christmas: Miracle on Third Street" is this for the three main teachers, taking place right after the Christmas Episode "Yes Mikey, Santa Does Shave". In the episode itself, Principal Prickly only appeared in two scenes, Miss Finster appeared in the same amount of scenes but had even less dialoge, and Miss Grotke only appeared for a few seconds.
The Avengers: Earth's Mightiest Heroes has an episode, "To Steal an Ant-Man," which consists almost entirely of Iron Fist and Luke Cage (who had never appeared in the cartoon before this point) fighting criminals. None of the Avengers appear except for The Wasp, who only does so during the first three minutes, and ex-Avenger Hank Pym, who had enlisted the two Heroes For Hire to hunt the man who stole his former crimefighting equipment. Hank gets some additional Character Development in this episode, giving it some connection to one of the show's main plots.
"New Avengers" provides an even better example: Kang the Conqueror traps the Avengers in another time, so Iron Man calls some of their crimefighting allies (including Spider-Man, War Machine, The Thing, Iron Fist, and Luke Cage) to form their own superhero team. These heroes (plusWolverine) try to work out their differences and try to stop Kang from taking over the world.
The entire Transformers Rescue Bots show could be regarded as a Lower Decks series, as it depicts the adventures of four junior Autobots who are not yet experienced enough to join the battles occurring concurrently in Transformers Prime.
The Aladdin: The Series episodes "Rain of Terror" and "Power to the Parrot" don't feature Aladdin or Jasmine as the main characters, instead focusing on Genie, Abu and Iago. Well, in "Power to the Parrot", it does feature Aladdin and Jasmine, but they are Demoted to Extra and barely have any lines, let alone an impact on the plot, and become Plucky Comic Relief.
The Quack Pack episode "All Hands On Duck" doesn't feature Huey, Dewey or Louie. It instead focuses entirely on Donald.
The Lion King 1 1/2 (or 3: Hakuna Matata) is the Lower Deck version of The Lion King, telling the story from Timon and Pumbaa's point of view.
The Looney Tunes Show has "Ridiculous Journey" which is a roadtrip involving the "pet" characters journeying home ala Homeward Bound while meeting other Looney Tunes characters that haven't been used in the show before, instead of the regular cast of Bugs and Daffy.