History YMMV / ACertainScientificRailgun

** Mikoto has a dream where she's Misaki's maid and has to do things like give her a massage. It is implied that Misaki had the same dream, but in reverse. And of course there's the groping incident shortly afterward...

** The MISAKA Network dorkiness, especially considering that many of them are gonna get brutally killed off.

** In Season 2 of the anime, Mikoto's side of the Sisters arc takes 15 episodes (episode 2 to episode 16). While it is widely agreed to be better than the [[LightNovel/ACertainMagicalIndex Index]] version of the same arc in nearly every way, the fact remains that the majority of the audience already knew exactly what was coming, so it was a bit frustrating it was dragged out so long.

** RescuedFromTheScrappyHeap: Uiharu managed to win back a lot of her detractors by defying [[spoiler:Kakine]] and protecting [[spoiler:Last Order]] in the main series ''Index''.

* AudienceAlienatingPremise: A major theme of the "Level-Upper" Arc revolved around the resentment of lower-level espers (Levels 0-3) towards higher-level ones (Levels 4-5), falsely believing that high level espers looked down upon them or oppressed them. While most shows aimed at young demographics would turn this into an anti-bullying message, ''Railgun'' instead takes the "being oppressed is all in your head" approach, which is often a lot more contentious.

* FunnyAneurysmMoment: Chapter 47 of the manga, adapted to episode 3 of ''Railgun T'', features the first time in the franchise that Touma is seen interacting with Misaki Shokuhou. Aside from the fact that Misaki somehow already knew Touma's name, the meeting is played up in a humorous manner, with Misaki acting silly and Mikoto casually being mocked. However, around two and a half years after this chapter released, Volume 11 of ''New Testament: A Certain Magical Index'', came out, revealing Misaki's backstory with Touma, including how tragically Touma can't retain memories of her due to brain damage. This puts that meeting in ''Railgun'' in a new light: Misaki suddenly re-encountering the boy she has feelings for, a boy that she knows will never retain memories of her. And not only that, she is with her rival, who also has been regularly interacting with that same boy as of late. It's not a surprise that after episode 3 of ''Railgun T'' aired, sales of ''New Testament'' Volume 11 shot up.

** Misaki Shokuhou was initially hated by the fanbase for her very manipulative personality, especially in her appearances in Season 2 and the first half of Daihasei Festival Arc in Season 3. One particular scene that made the fandom mad at Misaki was when she erased her memories of her friends, [[spoiler:which is later revealed to be her measure so that Mikoto's friends will not intervene in her plans to take down Gensei]]. Manga and light novel readers also reacted this way, but their hate for Misaki subsided much earlier than anime-only viewers, as the manga and light novel revealed her true intentions, [[spoiler:as well as her connections with Dolly]], in the latter half of the arc much earlier.

* MorePopularSpinoff: While ''Index'' was a hit, ''Railgun'' was more popular, sold more [=DVDs=] and got a better reception with fans thanks to a lot of CharacterDevelopment for the cast. This is probably because it's also partially a SchoolgirlSeries. Furthermore, in a world where crazy people wields crazy superpowers that get thrown around with reckless abandon, the main characters of ''Railgun'' seem like relatable humans (see the case with Saten, above). Note however that this is only true of the ''Index'' anime. The ''Index'' novels sell hundreds of thousands of copies and are the most popular medium of the entire verse by a healthy margin.

* ShipSinking: Any fan with an interest in seeing Ruiko Saten and Frenda Seivelun get together had their ship sunk when it was revealed in the main series ''Index'' that [[spoiler:Shizuri Mugino killed Frenda in Battle Royale arc, and Saten not knowing anything about it]], though [[spoiler:Saten]] may have her suspicions that [[spoiler:Frenda]] will never come back to her.

* ShipSinking: Any fan with an interest in seeing Ruiko Saten and Frenda Seivelun get together had their ship sunk when it was revealed in the main series ''Index'' that [[spoiler:Shizuri Mugino killed Frenda in Battle Royale arc, and Saten not knowing anything about it]], though she may have her suspicions that [[spoiler:Frenda]] will never come back to her.

** In Season 2 of the anime, Mikoto's side of the Sisters arc takes 15 episodes (episode 2 to episode 16). While it is widely agreed to be better than the Index version of the same arc in nearly every way, the fact remains that the majority of the audience already knew exactly what was coming, so it was a bit frustrating it was dragged out so long.

** Saten's trademark inspection of Uiharu's panties. Plus, in the second half of the second season, they essentially adopt a child together.

** Gensei's [[spoiler:granddaughter]], [[BitchInSheepsClothing Therestina Lifeline]], is just as cruel and twisted. Wanting to follow Gensei's example, Therestina abducts children and puts them in comas so she can harvest the samples from their minds. Gensei manipulates the young heroines into providing cover for her, all the while intending to overload the minds of the children she keeps under sedation, fully aware this will destroy all of Academy City and not caring as long as she achieves the "perfection" she hungers for.

* HarsherInHindsight: The MISAKA Network dorkiness, especially considering that many of them are gonna get brutally killed off.

** Misaki Shokuhou was hated by the fanbase for her very manipulative personality, especially in her appearances in Season 2 and the first half of Daihasei Festival Arc in Season 3. One particular scene that made the fandom mad at Misaki was when she erased her memories of her friends, [[spoiler:which is later revealed to be her measure so that Mikoto's friends will not intervene in her plans to take down Gensei]]. Manga and light novel readers also reacted this way, but their hate for Misaki subsided as much earlier than anime-only viewers, as the manga and light novel revealed her true intentions, [[spoiler:as well as her connections with Dolly]], in the latter half of the arc much earlier.

** Gensei's [[spoiler:granddaughter]] [[BitchInSheepsClothing Therestina Lifeline]] is just as cruel and twisted. Wanting to follow Gensei's example, Therestina abducts children and puts them in comas so she can harvest the samples from their minds. Gensei manipulates the young heroines into providing cover for her, all the while intending to overload the minds of the children she keeps under sedation, fully aware this will destroy all of Academy City and not caring as long as she achieves the "perfection" she hungers for.

** Mikoto has a dream where she's Misaki's maid and has to do things like give her a massage. It is implied that Misaki had the same dream, but in reverse.