When a work has a large and active fan base, but seems to be virtually unknown by mainstream audiences, who are often surprised the work in question has a fanbase at all, much less such a large one.
Essentially an inverse of Mainstream Obscurity. Where a work suffering from Mainstream Obscurity has had a huge influence on popular culture and is often referenced by all kinds of people, but has a comparatively small fan base who have actually seen/read/played the work in question, works suffering from Obscure Popularity are almost never referenced in the mainstream, and don't seem to ring a bell for a lot of people not actively involved in the fandom, but said fandom actually has a lot of members.
Might overlap with First Installment Wins, when mainstream audiences know about the original incarnation of the work, but are unaware that there are newer incarnations of it. Related to Americans Hate Tingle and Pop-Culture Isolation.
- Pokémon Adventures is one of the most best-selling manga in the world but is rarely talked about even amongst the Pokémon fans. Forums and fan-sites prefer to focus on the anime. The little exposure the manga usually gets either talks about the original Kanto (and maybe Johto) arc or contrasts it with the anime by calling it "better" because it's Darker and Edgier and Truer to the Text.
- Yuyu Hakusho was a very famous anime from The '90s and only Shonen that could rivalize in its time with the big success of Dragon Ball Z in Japan. But the success was predominantly in Japan. It was influential in the 1990s English-language anime Newbie Boom but never reached the popularity levels of works like Ranma 1/2, Sailor Moon, or Pokémon. It became obscure in the 2000s and was later overshadowed in the 2010s by the second (and most successful) creation of Yoshihiro Togashi: Hunter × Hunter. Even with the worldwide distribution and translation during the 2000s (mostly thanks to Toonami that emitted the series in parts like USA and Latin America), only YYH fans discussed about this series nowadays.
- One Piece is this in America and the west in general. It was always overshadowed by fellow serialized works Naruto and Bleach over here, and thanks to the infamous 4Kids dub that butchered the original anime beyond recognition, it never really caught on in the western world. This despite being a behemoth multimedia franchise in its homeland.
- Archie Comics has been thriving for over 50 years in the American market, which is predominantly focused on superhero comics. The comic sells itself on nostalgia and being a fun, easy read for all-ages. It also helps that they're more accessible than a lot of other comics (which are usually found at comic book stores or online). Still, Archie's rarely gets discussed much exactly because they're so accessible and episodic; there aren't plotlines or character arcs to discuss. The only times the franchise gets mentioned much is when there's some sort of gimmick or quirk (such as the Gender Flip issue, the spinoff comics such as Life with Archie: The Married Lifenote and Afterlife with Archie, the Weird Crossover Archie Meets the Punisher, or the 2015 reboot).
- Erin Hunter:
- Warriors routinely sells well, has literally dozens of books spanning nearly two decades, has a series of comics, and has one of the largest fandoms among literature, yet its mainstream exposure is next-to-none. This is likely due to its premise as a Stray Animal Story.
- Warriors' sister series Seekers, Survivors, and Bravelands do well in sales but have almost no online exposure. They don't even have fandoms.
- Despite being a part of Marvel Cinematic Universe, Agent Carter isn't as widely known as the Netflix series (for example, Jessica Jones) and people are surprised it even has a fanbase as the series isn't as widely publicized as other Marvel series. When it is mentioned, it's usually about the main actress, Hayley Atwell, aka Peggy Carter, the main character.
- The Blacklist gets publicity in the U.S. and Canada and the United Kingdom, yet its fanbase is a small, dedicated one, and it's more often discussed on Reddit than mainstream with fanon and Fan Wank being popular there.
- Zig-Zagged with Police, Camera, Action!, which does have mainstream recognition, but is more known for piracy on torrent sites and lack of availability on streaming services. Yet, the show is well-known enough and was well-liked from 1994 to 2003 in the United Kingdom and then 2007-2008, before fading into obscurity in 2010 after the final series aired. It's also a Cult Classic too.
- Street Signs, a CNBC programme about financial markets (not roads or street signs, making it a Non-Indicative Name - the Street Signs, refers to Wall Street) is popular, and has some knowledge amongst the general public. It's more known for its Ms. Fanservice, although that aspect is downplayed.
- Nightcore remixes and music gets millions of views on YouTube and other websites, yet the genre is all but unknown outside of anyone older than their mid-20s.
- Vaporwave is popular online but hasn't caught the attention of mainstream media.
- A lot of people have collected Pokémon cards when they were kids, but eventually stopped. Nowadays, the Pokemon TCG is thriving, with thousands of people of all ages attending tournaments, and the cards themselves even outselling Magic The Gathering at times. Yet, a lot of people, even from within the greater Pokemon fandom, seem surprised not just at the popularity of the game, but the mere fact that it still exists to this day.
- Bakugan was a hit tabletop game for several years and had a popular anime, but it's virtually unknown amongst adults and kids not in the fandom. The anime suffers from frequently being looked down upon as a "ripoff" of other mon and card anime.
- Beyblade is popular amongst children, with several popular anime and a successful toyline of beys. Despite this, it's rarely mentioned for being anything besides "another one of the Pokemon clones" (alongside Yu-Gi-Oh and Digimon) and nothing but the first anime gets referenced.
- BIONICLE was popular enough that it helped save Lego as a company, went on for ten straight years, covered almost any type of medium even outside the main toyline, including books, comics, video games and four movies, even received an (admittedly less successful) reboot in 2016...but looking at what most people seem to think about it, the mainstream only seems to remember it as "that Lego thing with the colored robots", with a lot of people not even being aware of the greater plot, or any of the sets past the first movie.
- Digimon toys are considered the More Popular Spinoff of Tamagotchi in terms of sales, but Tamagotchi is routinely referenced while the Digimon toys are not. Even the popular anime series' haven't shaken off the stigma of being a "Pokémon clone" and many don't even know there was anything outside of the first two anime.
- Homestuck is arguably one of the most famous works on the animation and gaming parts of the internet... and nowhere else, really. In spite of its enormous fanbase, nobody out of the internet knows about it, and even show it'll be very hard to find someone talking about Homestuck out of the dedicated or related forums.
- Pewdiepie was the most subscribed Youtuber for several years in a row and his videos regularly get at minimum 2 million views each. This success hasn't correlated into being a celebrity. He has little mainstream discussion outside of a South Park episode featuring him and a few news articles about him being a negative influence on kids.
- This seems to apply to YouTubers in general. Even if they have hundreds of millions of subscribers and views, YouTubers are rarely, if ever, mentioned in mainstream media unless they either break into the mainstream (i.e. Justin Bieber) or are caught in a scandal of sorts.
- The Truth About Cars, an automotive blog, isn't widely known outside automotive circles, but does have a large fanbase. However, it was mocked mercilessly on the Facebook pages of Little Mix and Ariana Grande by fans of those pop stars for being seen as Lurid Tales of Doom (although there is no evidence to support this claim), so this trope is Zig-Zagged somewhat.
- Jacksfilms has been a YouTuber with a ton of success, having a steady growth of subscribers, consistent video views, and even a ton of collaboration videos with more famous YouTubers, like the most popular YouTuber himself, PewDiePie; however, despite his consistent success and connections with mainstream content creators, he's never one of the YouTubers given much spotlight, such as not being featured in YouTube Rewind and not being discussed much outside of his own fanbase.
- SuperMarioLogan has a huge and dedicated fanbase, and yet it's only known in the mainstream for the episode "Jeffy's Tantrum!" causing a young boy to try and hang himself like Jeffy did.
- Ninjago's fanbase is enormous, but it doesn't have much mainstream recognition, and is seen by most Cartoon Network fans as "that one show that's still airing for some reason". Not even the movie received much recognition.
- Thomas the Tank Engine is only known to the public as "that creepy British show about talking trains that had an episode where a train got sealed in a tunnel and has a memetic theme song". The news articles making completely false claims such as the show being 'fascist' didn't help matters. On the other side of the coin, the Thomas fanbase is enormous and passionate about the show. There are people who collect the toys, make their own custom toys, review episodes, make fan art (sometimes humanized), write fan fiction, recreate music from the show, etc. The fanbase is also incredibly diverse. Not only is Thomas popular with preschoolers, but its teen and adult fanbase practically rivals the bronies in size. There are American fans, Japanese fans, Spanish fans, etc, and even a number of LGBT fans.
- British actress Natalie Gavin, from Buttershaw, near Bradford, Oop North, in England, is not an A-lister. Not yet. However, she was interviewed by a major magazine, Northern Life. In the United Kingdom, she has quite a fanbase, but is known more for her acting, rather than any controversies, as with individuals like Miley Cyrus or Russell Brand, and people are surprised she even has one. People know her from dramas such as Line of Duty (BBC).
- Juliana Tatelbaum, German-born presenter of CNBC series Street Signs is popular, with a substantial fanbase, but she isn't widely known outside of CNBC fans. Like the above example, she is known more for her work than any Scandal Gate controversies.