Between the vast and colorful supporting cast and the sheer size of the fandom, there are plenty of My Little Pony: Friendship Is Magic characters whose fans consider them underutilized. When the series is a combination of Merchandise-Driven and Long Runner, is it any wonder?
Note: This list applies as of the Season 9 finale "The Last Problem" and mainly focuses on characters from the main show. Examples for My Little Pony: Equestria Girls and the 2017 movie are to be in their own respective example lists.
- Almost everything about Princess Luna (sister of Princess Celestia, rules the night, became a Mad Goddess because of loneliness and jealousy, sealed in the moon for a thousand years) could be the basis for numerous stories, but after Twilight and company purged her of evil and she reconciled with Celestia, she wasn't even mentioned again for the entire first season. Since then she's had A Day in the Limelight and a few cameos, but they only succeeded in introducing and hinting at more traits that could be explored. It's no mystery that she is the most popular Ensemble Dark Horse of the fandom.
- Luna's villain persona Nightmare Moon had everything a villain needed: a cool design, a clear motive, and even henchmen. Unfortunately, bringing her back would completely undo the Character Development that Luna has since gone through. Season 4 got around this problem by featuring a return from Nightmare Moon... in the form of a flashback Twilight gets of the night she was banished to the moon. She also receives some screentime in the form of an alternate timeline in the Season 5 finale.
- King Sombra, out of all the main antagonists — if not out of every single antagonist in the show, or even any character period — is the only one who has had no opportunity to experience any character focus, despite being highly competent and frighteningly dangerous. With little interaction with the mane cast, barely any dialogue, very little screen time, he was written as more of a mindless beast than an actual villain. There was evidence to suggest he was going to be the show's first recurring villain, until the official comic used Queen Chrysalis to fill that position. This was somewhat mitigated with him not only getting the longest Bad Future scenario in the Season 5 Finale, but also being played as one hell of a scary villain as opposed to the Advancing Wall of Doom characterization he got in his first appearance. He finally comes back in full form in the Season 9 premiere, though fans were divided over how he was portrayed.
- Celestia, although she appears in numerous episodes, never receives any character focus like Luna and exists mostly to provide exposition. What hints do exist as to her past and personality — especially the ones that might indicate she's wearing a Tough Leader Façade — are tantalizing enough to make her a prime target for fanfiction writers, but they're only hints and near nothing is really known about her. Celestia fans are quite irked that she seldom gets to do anything, that when she does she gets soundly stomped to the curb so the Mane Six can save the day instead, and that she had next to no screentime in the Season 5 Premiere and Finale. In Season 7, Celestia finally gets her due, sharing the spotlight with Luna and finally revealing how difficult their respective jobs are, and she finally gets an episode to call her own in Season 8 when she's championed to act in a play in spite of being a god-awful actress.
- The Pony of Shadows (Stygian) despite having an amazing design and backstory, is the least recurring antagonist of the entire series, appearing in only two episodes late into the season seven finale. His redemption arc came too fast resolving all conflict.
- Peewee, a baby phoenix who Spike appeared to adopt at the end of the episode "Dragon Quest". This had a lot of potential: it gave Spike a pet like the rest of the Mane Cast, not to mention a friend who'd live as long as him. The next time he's even mentioned since his introduction? Finding out he's been Put on a Bus offscreen! Makes you wonder why they even bothered introducing the character. He finally returns from his Long Bus Trip in "Molt Down"...only for a brief cameo that doesn't contribute much to the plot.
- Spike the Dragon was accused of this in the show's early days. He's shown time and time again to have some quite amazing abilities, from swimming in lava to fire breath that can melt locks or stadium-sized pieces of ice, Hidden Depths, and a rather mysterious backstory due to no one knowing exactly how Celestia ended up with his egg to begin with. But in the episodes where he even makes an appearance he's either thrust into the background or serves as a source of comic relief. Starting with Season 6 he gets more opportunities to shine, notably with "Gauntlet of Fire" and "The Times They Are a Changeling", and from that point the writers started treating him less as comic relief and more as a main cast member in his own right.
- Babs Seed who was inducted as the fourth Cutie Mark Crusader at the end of "One Bad Apple", opening up a flood of possibilities for her to crusade either in Ponyville or her hometown of Manehattan. Her next appearance later in the season briefly mentions her new life in Manehattan and making friends with two other blank flanked foals. After that, she was Put on a Bus until early on in the fifth season where it was revealed (off-screen, no less) that she got her cutie mark. Eventually, the show pretty much forgot about her.
- Shining Armor was introduced as Captain of Canterlot's Royal Guard and a Cool Big Bro to Twilight Sparkle. One would expect him to be a capable fighter and to provide strong emotional support to Twilight, but in his appearances he gets beaten easily by the current villain and has little role beyond "Cadance's husband" (and even then, he and Queen Chrysalis get more screentime as a couple than he and Cadance), if he isn't just treated like a background character. He's gotten more appearances as the show's gone on, but very rarely gets to be anything more than the Monster Of The Weeks casualty or just the brother/husband/father of the starring alicorn princess. It took revealing a nerdy side to him in "The One Where Pinkie Pie Knows", panicking about being an upcoming father in "The Crystalling" and being the antagonist in the 200th episode "Sparkle's Seven" that we actually see other sides of his character. These examples would have got him disqualified for this list if wasn't for the fact that all these aspects were barely or never followed up upon until the show's end.
- Princess Cadance is the third princess to be introduced, having known Twilight since childhood. She can use the Magic of Love to bring people together and fell in love with Shining Armor. Seven years later that's about all we know about her going off the show. Other aspects of her past, her life before becoming a princess, Celestia raising her as a niece, and any other aspects of her character are glossed over in supplemental materials. Despite having the most in common with Twilight among the other princesses, this is rarely touched upon if it all and she mostly just stands with the other ruling princesses or gets defeated by the story's current villain. Even her special talent is rarely referenced or demonstrated after early appearances. This sticks throughout the entire animated series. All 9 seasons of them.
- Silver Spoon has gotten little characterization beyond being Diamond Tiara's Beta Bitch for the bulk of five seasons and dropping her like a sack of rocks once she starts treating her the same way she treated everyone else. Quite a few fans are wondering what she's like when Diamond Tiara isn't around.
- Similarly, Diamond Tiara has gotten to do exactly nothing beyond appear in a few background shots since her reformation, leaving many fans to wonder why the writers even bothered to have her and Silver Spoon befriend the Cutie Mark Crusaders if it just meant they would be swiftly forgotten as characters.
- Jim Miller would confirm a month before the series finale that the writers wanted to do more with her and Silver Spoon, but the higher ups thought that "their story was done".
- Suri Polomare is a rival and old acquaintance to Rarity. It is implied that she has made bad experiences in Manehattan (just like Rarity) which made her the shifty pony she is now. There could be a great story for a redemption that has yet to be told.
- The Mean Six. Introduced in the eponymous episode, and had the potential to be an interesting Quirky Miniboss Squad, with Mean Twilight being smart enough to become a major threat. Instead, they're destroyed outright in their debut episode, and the Mane Six never even realize they existed. It feels like even more a waste coming off of the tail end of a season that dealt with themes of specism: ponies that were not "real" appearing after Twilight had firmly established her beliefs on accepting other species could have posed an interesting challenge to Twilight's beliefs and forced her to reconcile the "they're not real so we can destroy them" attitude she had with the Pinkie Pie clones with her "friendship is the right of every creature" stance she had fought Chancellor Neighsay on. It's especially bad as Queen Chrysalis continued to hang onto the hunk of wood that was left behind when Mean Twilight was killed well into Season 9, which taunted audiences with the possibility that she might make a return that never happened.
- The EEA. They are revealed to the department responsible for the education of Equestria. However, the other members with the exception of Neighsay were never fleshed out beyond being Spear Carriers. Being never mentioned again after Season 8 really didn't help matters.
- Zecora. Originally planned to be Twilight's second mentor, her entire significance to the overall narrative practically fell off a cliff as that role wound up being scrapped practically entirely save for one episode. Over the seasons, she was reduced to a MacGuffin dispenser whose significance is defined by what potion she cooked up to serve the episode's plot. Outside of that, we practically know nothing else about her to the extent that not even Word of God can confirm that Zebras as a race even exist in Equestria. The Season 10 comics would avert this as its first Story Arc features the heroes visiting the Zebra homeland and exploring Zecora's past.
- The Pillars of Equestria. Precursor Heroes who defended Equestria before Celestia and Luna. Outside of that and their Origins Episode, we barely know anything else about them. Not only that, outside of showing how Starswirl and Rockhoof adapted to the modern world, the others just settled down offscreen with a quick "Where Are They Now?" Epilogue and were never mentioned again until the series finale in which they got defeated very quickly while barely contributing to the plot. If it wasn't for their own contribution to the final attack, you can write them out of the episode and you wouldn't miss anything important.
- The REAL Grogar. In light of the one we have been seeing being a persona of Discord all along, we have practically no idea who really is he and how much of his supposed backstory is true. The fact that we know about his bell more speaks volumes.
- Prince Blueblood is Celestia's nephew about 52 times removed on her mother's side. Outside of being a Prince Charmless to Rarity in the Season 1 finale, we know next to nothing about him despite being literally a Prince. He was shown in a cameo in "Sweet and Elite" next to Rarity and that's it. With Princess Cadance away in the Crystal Empire, he could have acted as a teacher of royal court life for Twilight in the later seasons. However, outside of a comic book issue, he practically disappeared from the show.
- Many of the one-shot races like the Diamond Dogs, Buffalo, Saddle Arabians and Kirin never got much of a showing after their debut episodes.
- Much like Princess Luna and the Pillars of Equestria, the Crystal Ponies are time displaced individuals suddenly thrust in the modern day. On top of this, they were also enslaved by a tyrant and live in a mysterious city far away from Equestria proper. None of these plot threads are addressed or explored in the series proper. Only that they shine when happy.
- The family members of the Mane Six are usually subject to A Day in the Limelight but these particular examples aren't so fortunate.
- The Pie family, minus Pinkie and Maud. While Igneous Rock and Cloudy Quartz play a more prominent role in Pinkie Pie and the Rockin' Ponypalooza Party and later made major reappeareances in the season 5 episode "Hearthbreakers" along with Pinkie's other two sisters, Limestone and Marble Pie, not much is known about them other than they are essentially pony versions of the Amish who are highly conservative, strict, old-fashioned and speak in archaic english, not to mention their story is seemingly tied to an ancestor who gave them Holder's Boulder, a huge rock formation resembling a dragon's egg, as a gift. Why they farm rocks in the first place or if there are other families like them is never elaborated upon, and neither the series nor the comics have really touched on them. As for the other two sisters, Limestone is established as being in a perpetually wrathful mood, which is implied to be the result of the stress of working on the farm and not getting the chance to travel and explore the world as Pinkie and Maud do, and Marble is such a Shrinking Violet, she can only say "hmmm" and even makes Fluttershy look like the most confident and daring equine in Equestria. Sadly, the other two Pie sisters haven't really been explored as well.
- Rarity and Sweetie Belle's parents. Their only major role is a very brief appearance at the start of Sisterhooves Social. Both are radically different from Rarity and she seems to consider them Amazingly Embarrassing Parents, but we never really find out what their relationship is like. This especially sticks out because the rest of the Mane 6's parents got at least one spotlight episode. (Even Applejack's, who are Posthumous Characters)
- Twilight Sparkle's parents. Much like Rarity's parents, they barely speak at all and are constantly in the background in any episode they star in. The closest we ever get was "Once Upon a Zeppelin", in which Twilight Sparkle's mother, Twilight Velvet is so eager that she essentially signed her whole family off as a product without even realising it and is an adrenaline junkie. However, any role she and her husband play is pushed to the background after that for Twilight's screentime.
- Thorax and Ember. Outside of their established characterization in debut episodes while learning to be good rulers of the Changelings and Dragons respectively, we don't know much else about them.
- The Tree of Harmony. A ancient and sapient tree that is responsible for the creation of the Elements of Harmony after the sealing of the Pillars, has roots that spread to the School of Friendship's basement, is the (unofficial) Guardian Angel/Good Is Not Soft/Sink or Swim Mentor of the Young Six and the Greater-Scope Paragon of Equestria or even the world. Outside of appearing in front of the Young Six in an astral projection of Twilight Sparkle to issue exposition or tests, we never see it interact with any other notable individuals like the Mane Six, so that's all we know about it. After being rebuilt into the Treehouse of Harmony, it never appears for the rest of the show. It doesn't even appear in the finale as part of the Young Six's Big Damn Heroes moment where they rallied practically all of Equestria to help fight.
- Fleur de Lis is regarded as a gorgeous upperclass pony in Canterlot and mostly seen hanging around Fancypants or just spotted in Canterlot, but has had little to no time to be explored to see how she views others and what she even does for a living. She's only had one speaking line in her debut episode in season 2 but has never spoken another word again.
- Sapphire Shores is a popular singer in-universe and is well talked about by Rarity and the Cutie Mark Crusaders. Unlike other music-themed characters like Songbird Serenade and Coloratura, we never hear her sing once.
- Spitfire and the rest of the Wonderbolts are criminally underutilized in the series. Spitfire appeared at least Once a Season, but most of her roles were limited to maybe one scene an episode with maybe one or two lines of dialogue at most. Even after Rainbow Dash joined the team, next to no time was shown of her working with them for much of the show, with their appearances still being limited all the way to the end of the series, something that could have used more of to show them working with Rainbow and getting some more characterization. The Season 10 comics give a Lampshade Hanging on this, as in #89 when Spitfire is among the cast that's been gathered by Twilight Sparkle, she shows surprise because in her words, "Twilight never calls me for any of the cool stuff."
- Sugar Belle, Party Favor, Night Glider, and Double Diamond in Season 5 premiere were the only members of Starlight Glimmer's cult with full characterization, interaction with the Mane Six and Starlight, and played an equal if not greater role in saving the day than the heroes, suggesting they would become major characters. But they only had a few minor appearances by the Season 6 finale, never explaining what made them decide to join Starlight's cult, how/why the former three wished to rebel against it despite their submission and Double Diamond became Starlight's right-hand pony, or what made them decide to forgive Starlight even after she took away their individuality and freedom. Subsequently, only Sugar Belle would get a prominent role as Big Macintosh's Love Interest, leaving the remainder of her history with Our Town unfathomed while the rest were limited to cameos.
