- Acting for Two: The eponymous Liz and the Blue Bird share the same voice actress. This is true in both the original Japanese (Miyu Honda) and the English dub (Courtney Shaw).
- Casting Gag: Liz and the Blue Bird casts Cristina Vee as Reina, the Aloof Dark-Haired Girl and The Ace of this KyoAni project. Sound familiar?
- Cut Song: Several songs on the official soundtrack were not used in the film. Unusually for an anime, the score was completed early on, and the animation was closely tailored to it, which is likely why certain songs were unused.
- Dark Horse Casting: Alongside the usual cast of Sound! Euphonium, Liz and the blue bird are voiced in the Japanese version by Miyu Honda, a child actress who was 14 years old at the time. She's known mainly for acting in live action programs, with little experience in voice acting (though she had previously voiced Sophie in the Japanese dub of The BFG). This film remains her only anime voiceover role to date.
- Directed by Cast Member: The English dub was directed by Stephanie Sheh, who also voices Nozomi.
- Promoted Fangirl: Cristina Vee mentioned on a Twitter post that she absolutely loves Eupho and really wanted to play Reina, and was ecstatic when she found out she got the part.
- Uncredited Role: The English dub actor for Kumiko was left uncredited in the initial cast list. The dub's director, Stephanie Sheh, would later share on Twitter that she's voiced by Courtney Shaw
(who also voiced Liz and the blue bird, and is credited for those roles).
General Trivia
The piece Liz and the Blue Bird, written for the film, is a full 20-minute orchestral suite with four movements. However, the full piece is not played in this film, despite being the namesake and basis of its plot. The film focuses on the third movement, "The Things We Do for Love," which is centered around the flute and oboe duet that Nozomi and Mizore play. Excerpts from the other movements are played during the storybook segments. These excerpts, alongside the whole suite, are included on the film's original soundtrack, while a truncated 8-minute version of the suite is played in 2019's Our Promise: A Brand New Day.
