Harry Du Bois’s review published on Letterboxd:
I'm pleasantly surprised that DC animation movies can actually be brooding, patient with its punches and thought-provoking!
The Long Halloween Part 1 is a solid film, showcasing the best that detective-centric Batman stories can be — fascinating characters, an intriguing and engaging narrative, fun interactions, and so on. The voice cast do wonders to bringing their characters and the city of Gotham to life, especially Jensen Ackles and the late Naya Rivera. I wish they pulled more inspirations from the original comic in terms of art style, but who am I to say? The animation isn't so generic (as opposed to, erm, most-to-all other DCAU movies) and the muted, dimly-lit colors fit the tone of the story perfectly.
As a part one in two-part story, all I can say for now is that I'm genuinely excited to see how the story progresses. Though I should say, the identity of the Holiday killer is perhaps a little bit too obvious for even the unknowing moviegoer (namely me).