Due to his sheer badassery and that one costume he used in the training montage end, Genjuro is affectionally called Akuma.
Chris's song Mayumi Ichii-Bal has her repeatedly singing "zenbu", so fans have often taken to referring to her as Zenbu.
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).
Both Shirabe's relatively serious nature and Weapon of Choice have earned her the nickname Buzzkill.
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.
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.