Alternative Character Interpretation: Is Boogiepop an entity that happens to possess Touka whenever it is necessary? Or is Boogiepop just some alternate personality that Touka developed out of the stress of her parent's then troubled relationship? And how much does Touka know or not know about her connection to Boogiepop? In-and-out of universe these questions are debated and ultimately subjected to one's own opinions. Nagi and Takeda (to a degree)at least seem to consider Boogiepop a split personality of Touka's, while Boogiepop considers himself to be entirely seperate from Touka.
Complete Monster: Makiko Kisugi, the Fear Ghoul, is a psychiatrist and Serial Killer who terrorized the city five years before the pillar of light was created. Finding the evolution drug inside Nagi's room at the hospital, Kisugi tested it on rats and herself, gaining the ability to sense the fear in others. Discovering that she liked the taste of fear, Kisugi began scaring her patients in the worst conditions, and murdered five young, strong-willed girls by removing their brains while they were still alive, and stalked a sixth would-be victim, because "their souls taste better". Having manipulated Pigeon, Kisugi broke Mo Murder's spine and threw him off the hospital balcony, killing him. The anime explores even more of her crimes, as she had injected her patients, and her own pregnant friend with the drug, just to see what would happen.
First Installment Wins: The first volume, Boogiepop and Others, is by far the most known chapter of the saga, with Boogiepop at Dawn possibly coming behind on the basis of being its Prequel. It doesn't help that the English translation of the novels never went further than Dawn, and that the first anime series of the franchise, Boogiepop Phantom (which for many years was its only anime), was precisely a continuation to those two volumes.
They Wasted a Perfectly Good Character: It's almost comical how irrelevant Touka is to the plot other than being the host or a split personality of Boogiepop. It's telling when Takeda, who is kept deliberately Locked Out of the Loop and clearly intended to be her Satellite Love Interest, has more relevance to the plot than she does. It's worse in the anime where multiple episodes go by without her making an appearance or having any speaking lines.
Awesome Music: As it is usual in adaptations of the franchise, the soundtrack of the anime is always cited as one of its strongest points. Aside from Kensuke Ushio's work in the episodes themselves, MYTH & ROID's opening theme "Shadowgraph" and Riko Azuna's ending "Whiteout" were considered some of the best of 2019.
Better on DVD: The arcs' many characters and complicated plots make them much easier to understand when watched back to back. The producers of the anime seemingly realized this themselves, as they got several of the episodes (1-2 and 10-13) broadcast together as combined TV specials.
Broken Base: Fans were divided about how good of an adaptation the anime was, especially due to the compression of some of the novels' events. However, most were unanimous in that the series' production values, soundtrack and direction were quite solid.
Can't Un-Hear It: Aoi Yūki as Boogiepop. While not entirely faithful to the novels, being significantly more expressive and humanlike than described, her performance is considered by many to be the definitive take on the character.
Critical Dissonance: Critics praised the series for its brainy and artsy nature, while viewers and fans of the novels, if still decently positive, were more divided, the latter on adaptation issues and the former due to the whole Mind Screw.
Gateway Series: Because Boogiepop Phantom can only be understood by knowing the first volume's events, which were only adapted in an obscure movie in 2000, the 2019 anime was considered the first accessible adaptation to the complex Boogiepop universe. A whole wave of new fans and readers were made through this series.
Captions of Boogiepop's smug face were popular reaction shots during the anime's run.
The climactic scene of King of Distortion, in which Tanaka falls from the sky and smiles halfway down, is also used as a reaction gif.
Nightmare Fuel: Shinjiro Anou being painfully brainwashed by Spooky E is already enough, but Yoshiaki Hasegawa's voice acting as Shinjiro completes the scene with some absolutely bloodcurling screams.
Signature Scene: The scene with Tanaka falling from the sky became so notorious in the 2019 winter anime season that it remains known even among people who don't know the Boogiepop franchise in the first place. Ironically, the grandiosity of the scene is actually original to the anime; in the light novel, the whole fall occupies a single linequote "...and then his entire body crumpled to the ground." and there is no drama or mid-air realization as portrayed.
