- Fandom Nod / Ascended Fanon: A minor one. The Tokiwadai Dorm supervisor's appearance changes from the Index anime to the Railgun anime. Some fans think it was change to match her looks in the manga while others think they are just two different people with the same job. Along came Episode 19, which mentions there are two Tokiwadai Dorms, which suggest there are indeed two different dorm supervisors.
- Fan Nickname:
- From the 2nd Railgun mini light novel "Loli Kihara", aka Nayuta Kihara, a little girl who happens to be a Kihara.
- Fans have also taken to calling Heaven Canceler "Dr. Gekota" from Episode 10.
- Flip-Flop of God: In the beginning of the Index novel and anime, Mikoto fires a railgun which passes by Touma but in the Railgun manga drawn by Motoi Fukuyama, she fires the Railgun at him which he stops using Imagine Breaker. Unfortunately, this caused some backlash with fans since it is contested by the fandom if this is possible. To avoid this contradiction, the Railgun anime has the events that lead to the Railgun incident Retcon to an earlier date before the time of the first Index arc.
- Hey, It's That Sound!: In episode 16 of the first season of the anime, the cellphone of Kurozuma Wataru (who is actually Hebitani Tsuguo goes off. If you listen to the ringtone you find that the song playing is auld lang syne.
- Name's the Same: Ruiko Saten's surname is the same as a very different character in NEEDLESS, which led to some funny fanart.
- Pigeonholed Voice Actor:
- Playing Against Type: Colleen Clinkenbeard as the psychopatic Therestina Lifeline.
- Brad Hawkins and Katsuyuki Konishi as Wataru Kurozuma. An Anti-Hero who likes a good fight.
- Relationship Voice Actor:
- Definitely NOT easy to spot unless you've been doing your research. Kanae Ito, who is the seiyuu of Amu in Shugo Chara! is the skirt flipping Ruiko Saten. Aki Toyosaki, who is Su, is Kazari Uiharu.
- They also play Nana and Momo respectively, twin sisters.
- Also Atsushi Abe (Touma's seiyuu) is Amu's friend, Kuukai in Shugo Chara!.
- Speaking of Aki Toyosaki, her fellow seiyuus, Satomi Satou and Minako Kotobuki who played as Ritsu and Mugi respectively in K-On! (which Aki also voiced in), with the former voiced Edasaki Anri, one of Kiyama's students in Railgun, who looks like a mini Ritsu and the later voiced Mitsuko Kongo;, who is not like Mugi in anyway except being rich, beautiful and gifted with a well-endowed rack on a sexy body.
- The Tokiwadai Dorm Supervisor in Railgun (the one who always breaks Kuroko's neck) is voiced by Hitomi Nabatame while 'her wife' Shizuka Ito voiced Kaori Kanzaki in Index.
- Frenda Seivelun, Saiai Kinuhata, and Misaki Shokuhou have worked together in another series called Love, Chunibyo & Other Delusions as Rikka Takanashi, Shinka Nibutani, and Kumin Tsuyuri, respectively.
- For English dub, Mikoto, Kuroko, Saten, and Uiharu are Wendy, Sherria, Juvia, and Lucy.
- Sequel Gap: Season 2 of the anime ended in 2013, but there wasn't a new season until 2020.
- Star-Making Role: Two of them:
- Talking to Himself: Brittney Karbowski as Misaka and the other clones. Justified since the latter were cloned based on her DNA.
- What Could Have Been: The author Kazuma Kamachi originally intended for Kuroko Shirai to be the main protagonist, but the studio asked him to use Mikoto instead.
- Visual Pun: In Accelerator's first battle (chronologically), MISAKA 00001 is holding what appears to be a variant of the Colt XSE known as the Rail Gun.
Trivia / A Certain Scientific Railgun