B-Team Sequel: The third season was animated at Studio VOLN.
Cross-Dressing Voices: Played straight in the English dub where Konekomaru Miwa, Nemu Takada and Karura are voice by females, but averted in the original Japanese version where they are voiced by males.
Overtook the Manga: At the time the anime aired, only 30+ chapters of the manga were even out.
In the English version, Shiemi's mom goes from being voiced by Mari Devon to Dorah Fine following Devon's retirement.
Series Hiatus: On July 2021, Kazue Kato announced on her Twitter account that she's putting the series on an eight-month hiatus so she can work on the manga adaptation of Fuyumi Ono's Eizen Karukaya Kaiitan. Earlier in that year, the manga was also put on a two-month break because she got exhausted.
The prototype for Blue Exorcist is in the anthology Time Killers, under the name The Miyama-Uguisu Mansion Incident. There are some similarities between the two, the most obvious being the demon concept.
Imagine Rin being The Gunslinger and Yukio being the Blue Exorcist! Kato-sensei originally planned for that to happen.
Shiemi's original concept was more gothic in design, dressed in Elegant Gothic Lolita and lived in a black tower.
Concept art shows that Takara was originally going to be a girl (and Word of God confirms in the character book), and there are two other characters that were cut from the cast. Also, the not-quite-final designs of the character are slightly different and hint at somewhat changed personalities.
on her Twitter account that she's putting the series on an eight-month hiatus so she can work on the manga adaptation of Fuyumi Ono's Eizen Karukaya Kaiitan. Earlier in that year, the manga was also put on a two-month break because she got exhausted.