Yoh Yoshinari has cited in interviews that Ursula/Chariot is his favorite character and the one he generally relates to the most out of the cast.
Producer Naoko Tsutsumi's favorite characters are cited to be Croix and the shopkeeper from the TV series.
Hiroyuki Imaishi's favorite character is stated to be Sucy. Fittingly enough, he was the one that storyboarded her spotlight episode in the TV series. This is also likely the reason why Sucy was heavily prominent in Space Patrol Luluco's crossover episode with Little Witch Academia. Seeing as the former is directed by him.
Sucy's background had shifted over time. Originally, Sucy was stated to come from a poor family and her biological mother and sisters were both shown in the Teri Terio manga. However, over the years, Yoshinari has stated that Sucy is an orphan who got abandoned by her parents, which was how she's depicted in the Keisuke Satō manga.
Amanda's home state has been prone to flip-flopping. During one of Trigger Q&A sections on 4chan's /a/ board, when asked on where Amanda came from, they suggested that she might come from Brookyln. However, at Otacon 2018, when asked again, they instead stated that she's from Texas, but than two years later in 2020, during their live drawing/Q&A stream for AX 2020 Lite, when asked again, after a bit of a debate between New York and San Francisco, they once again stated that she's from New York.note Though they made it clear that it's just an "estimated guess" and not a true confirmation, which combined with them debating on it prior, indicates that they still hadn't really pin down and thought about which state she comes from (which they downright stated during the aforementioned 4chan Q&A), which explains the flip-flopping.
Keep Circulating the Tapes: Thanks to Netflix's removal of them in late 2019, both of the shortfilms are no longer easily available to watch in the West and the only way to watch them legally would be to obtain either the physical release of the first film by Acttil, which is long out of print, hard to find and highly expensive to boot or the physical release of The Enchanted Parade, which does contain both of the short films and is much easier to get, but was only released in Japan and also isn't cheap to buy outside of the country. Even then though, both releases only contain the original Japanese dubs, so if you happen to prefer the English or other dubs, you're unfortunately out of luck.
Name's the Same: There is a real-life Diana Cavendish (no relation), whose youth and relationship with her polio-stricken husband Robin were adapted into the 2017 film Breathe. Claire Foy played the role in that film.
Although plans for Akko and Andrew getting together were scrapped, their voice actors Erica Mendez (Akko) and Lucien Dodge (Andrew) are a thing in real life.
From the Tweeny Witches universe: M, Magna & Qoo, and Atelia as Diana Cavendish, Amanda O'Neill, and Headmistress Miranda Holbrooke respectively.
In the Chilean Spanish dub. Akko, Sucy, and Lotte's voice actresses worked together in the dub of Jessica Jones (2015) as Robyn, Jessica Jones, and Patricia Walker, respectively. Not surprising, as both series are broadcasted on Netflix.
The official Panel at AnimeNEXT 2017 (and repeated at AnimeExpo) revealed the backstories for Sucy, Constanze, Jasminka, and Amanda, which couldn't be fit in due to time constraints. These details reveal a surprising amount of information regarding why and how the aforementioned four act the way they do. Some of these are serious, while others were jokes made up on the spot:
Sucy was left at an orphanage with nothing but a bottle of poison; Her obsession with toxins is a result of it being her only connection to her real family.note This is possibly creator trolling, but is plausible. Sucy being confirmed to be an orphan in the Keisuke Satō manga, adds to this being plausible.
Constanze was struck with a terrible illness as a child; In order to heal her illness, her soul was literally removed from her body, which rendered her unable to speak. That robot always standing around her or on her head? it contains her now disembodied soul. It explains why she got so mad after it was damaged.note This is most likely a joke, because Constanze was around long before the Stanbot: she built him in episode 12 or the middle of The Enchanted Parade. Constanze also spoked briefly in the last episode, solidifying this as just a joke.
Jasminka is possessed by a Hungarian demon that embodies gluttony; If she ever stops eating constantly while she's awake, the demon will either get out or start consuming her surroundings (or both).note This was largely thought to be a joke, until a chapter of the Keisuke Satō manga showed the results of her being forced to fast.
Amanda comes from a wealthy family whose former matriarch (Amanda's great-grandmother) was a powerful fortuneteller. Using her abilities, her family prospered in growing their business empire, but with the loss of such an advantageous ability, Amanda's family sent her to Luna Nova in order to make her a fortuneteller as well in order to keep said company prosperous. Obviously, Amanda wasn't exactly thrilled with this idea.note This is probably creator trolling, but is at least plausible and is heavily implied to be the case in the Keisuke Satō manga.
The Trigger Night Vol. 6 Event elaborated on the lore of the setting, detailing how closely magic is tied to trees, particularly Yggdrasil. Of particular focus was how this nature grants witches long lifespans, but that more powerful witches, due to the magic constantly flowing through them, eventually turn into trees themselves. Examples given included Woodward, Beatrix, and Jennifer of the Nine Olde Witches, Holbrooke's mother, and virtually every head of the Cavendish family. It was noted somewhat somberly that this is certainly Diana's eventual fate too.
Keisuke Satō's manga:
Ascended Fanon: Thanks to chapter 8 featuring a Perspective Flip for Andrew, readers got to see what was happening in Appleton before he left for Luna Nova, and confirmed the dynamics people have assumed about its students with Frank being an outlier for liking magic, Andrew being respected but aloof to magic, while Louis was more or less seen as a bit of a rival to Andrew and the leader of the anti-magic sentiment.
No Export for You: The bonus chapters were not included in the volumes and thus, were never released outside of Japan.