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Nightmare Fuel: Mawaru-Penguindrum
This series by Kunihiko Ikuhara started as a rather... weird but humorous show. But as time went on, the weirdness increased, and well...
In episode 8, Ringo serves Tabuki a drugged montblanc and attempts to rape him but Shouma shows up in time to stop her thankfully.
That look when she's dragging Tabuki away. It only lasts for a second, but... her eye...
Tabuki is this in spades, in episode 11. It's bad enough when Ringo's Love Potion actually works on him so he acts all suave and NOT like his normal Cloud Cuckoo LanderNice Guy self, but then he starts acting like a frog ("ribbit" included) and making really horrible Nightmare Faces... as well as when he also punches through a door to try and get Ringo back inside, presumably to rape her after she decides to not have sex with him.. Be Careful What You Wish For, Ringo...?
For some, Mario Natsume is FREAKING CREEPY. The first thing he said in the series is "SURVIVAL STRATEGY!", he has his own Penguin Hat, shows absolutely NO emotions otherwise, freaks the shit out of the otherwise Hot-Blooded Kanba when they meet without saying a single word, is the center of his sister Masako's "Project M"...
Even worse in episode 16. When he finally gets to talk some more, it's because his grandfather's spirit is using him as a Soul Jar. AAAAUUUUGH.
Episode 14. Yuri drugs and tries to rape Ringo. NO ONE COULD SEE THAT COMING. Even worse is how Yuri is VERY mentally broken at that point and does this while mentally repeating how much she hates herself due to her body issues and loneliness.
And then we have episode 15. First there's Ringo's extremely erratic behavior and words as she calls Shouma while drugged and about to be raped by Yuri, which causes Shouma to freak out. And then we have Yuri's past as the victim of a rather... special, to say at least, type of physical abuse (as well as horrible emotional abuse, and maybe sexual as well) from her terribly creepy father. Who also happens to bear some vague resemblance to Touga's rapist stepfather from the Revolutionary Girl Utena movie. GAH!
Episode 17 and 18 have Tabuki as the freaking Master of this as he goes from kind and slightly off-kilter school teacher to totally unhinged would-be killer who takes Himari hostage and almost gets her and Kanba horribly killed.