A sadder side to this is that both Tsubasa and her CV, Nana Mizuki, have similar issues when it comes to paternal abandonment and parental approval. Makes one wonder how many nerves it touched for Nana Mizuki to do GX E9.
Due to his sheer badassery and that one costume he used in the training montage end, Genjuro is affectionally called Akuma.
Tsubasa is a sword. Or Setsuna. Back in season 1 and G she was also called Sakimori ("sentinel").
Chris's song Makyu Ichaival has her repeatedly singing "zenbu", so fans have often taken to referring to her as Zenbu.
On a side note, some fans also combined this Zenbu with boobs becoming "Zenboobs." The reason was that her Symphogear shows her ample boobs off as well as visibly the biggest bust (although canonically Maria has larger bust (96 vs 90), but downplayed due to height differences).
Since she has blonde hair and her Symphogear outfit resembles that of a witch, Kirika is known by some fans as Dark Magician Girl (or DMG for short). She's also known as DESS, due to her Verbal Tic.
Both Shirabe's relatively serious nature and Weapon of Choice have earned her the nickname Buzzkill. Certain Image Boards also call her Jii~, after a well-known gif of her staring at the camera.
Because they're almost always seen together, some fans have taken to referring to both Kirika and Shirabe as DMJii, a combined pun on their individual nicknames listed above.
After Maria spent most of G out of the action due to angst, she picked up the Detractor Nickname of Useless or Useless Tentacle Woman (the latter due to her hair looking like tentacles).
Nastassja, due to her name being difficult to spell/pronounce, is usually just called Mom or Ma'am as she's called in-series, but she's also called Wheels sometimes.
Before GX even started airing, Carol had already been nicknamed ZUN girl or simply "the Touhou", for her frilly outfit and large hat.
Fans on the wiki gave the nickname "Airgetlam" for Serena's and later Maria's gear. This is based largely on a piece of information on an official source naming the gear 'The Silver Gear'. The name being a nod to Wild ARMs 2 is also speculated. Confirmed by Maria's activation song at the end of G.
Hibiki's father, since being officially introduced, has generally come to be known as Top Dad (mainly due to being an awful dad and for being introduced as a Dirty Coward and a loser).
Symphogay for the series itself in some circles, due to the large amount of ship tease and close relationships between the girls, with at least two pairs hinted as being more or less "official" (read: heavily teased). Apparently, even the seiyuu of the characters have commented on it.
God Never Said That: Contrary to popular belief, the show was not a 2 cour (26 episodes) run that was switched to 1 cour (13 episodes) midway. Symphogear was always intended to be one cour, it's just that there were too many ideas and they had to be cut out. You can read more about it here.
Some fans assumed that the Downer Beginning was just a Troll and that Hibiki is still alive. Some even thought of it already at the very beginning. Boy, they were right!
In season 2, Maria isn't Fine's reincarnation. Also, for all of Ver's seemingly Well-Intentioned Extremist propaganda of 'saving humanity from the Moon's fall'... he just lied his ass off, he just wants to save his own butt and the rest die for his amusement!
Hibiki and Kanade are also the names of the first two heroines of Suite Pretty Cure ♪, another music themed magical girl anime. The evil force Noise is also the name of Suite Precure's Big Bad. Second season adds up a new antagonist whose first name is Shirabe, which is also the last name of Suite Precure's final Fourth Cure. Another new antagonist, Maria Cadenzavna Eve shares the same first name with Suite Precure's Hibiki's mother.
Shinji Ogawa shares his name with the late veteran Seiyuu Shinji Ogawa (March 2015)
No Export for You: At least at first. G was never licensed to the west compare to the first season when it premiered back in 2013. However, with Crunchyroll's licensing of GX, they were able to bring both G and the first season with them.
Sleeper Hit: The first season did rather poorly in terms of Home video sales, due to it's budget problems. The singles and OST, however, sold well enough that a second season was ordered. Each subsequent season has done double the previous ones numbers in terms of first week Home Video sales.