- The beginning of Gaster's cruel experiments on the brothers; he straps Papyrus down and prepares to drill into his hand to attach one of the titular hand plates, all while internally monologuing how he won't let himself fail.Gaster: Can you move?Papyrus: N... no. It... it's hard to breathe. I'm scared.Gaster: *Shudders, and then stops*Gaster: Good. You should be scared of me.
- The comic ends on the whirring of the drill.
- The comic where Gaster performs a No-Holds-Barred Beatdown on Papyrus using blue magic, specifically so the two never use their own blue magic against him. Papyrus' screams run through the length of the comic as he's battered almost to bits, and Gaster acts completely apathetic while Sans begs him to stop.
- Many of the experiments Gaster conducts, even if most of them aren't shown on-screen. Enough of them is shown to see their after-effects, and many involve power tools.
- The goop monster that attacks Gaster and the boys in one of the later experiments. Unlike Gaster, it has no justifications for what it does outside of being "curious." One panel even has it snap Gaster's arm like a twig, and is disturbingly casual about it.
- After Gaster is erased, various characters start having nightmares featuring him in some way, albeit not in person—just as an unseen voice or a figure they're trying to get to. They all range from creepy to downright disturbing.
- Asgore's dream starts with him greeting someone invisible for tea, and based on Asgore's responses the person says more and more upsetting things like how Asgore can't remember him and must hate him, and it eventually features two panels filled with stylized text saying things like "IT HURTS" and "PLEASE NO" over and over. Asgore's tea cup starts to drip blood. And then he wakes up to find Papyrus there, just staring at him and glowing (albeit Papyrus was trying to help, but even Asgore is unsettled.)
- There's a comic where the erased Dr. Gaster seems to be trying to call Alphys on her phone, and it's a bunch of garbled speech, whispering her name, and then static before it cuts off.
- A later comic that shows how Sans and Papyrus' first meeting with Flowey went. Sans writes in his journal about how he keeps getting this feeling like he "dreamed" about bad things happening, but he can't remember what they were. All through the comic showing silhouettes of previous fights Flowey had with the two of them, with Sans or Papyrus getting gored, decapitated, or torn apart.
- When Gaster breaks Sans' eye. Not only is Sans permanently blinded, he also loses his ability to glow in that eye, leading to a lot of emotional problems since eyeglowing is very important to skeletons' mental health. The author also mentions that Gaster is also blind in one eye, but can still glow with it, meaning Gaster REALLY messed Sans up to break the eye to that point.
Gaster: Well, that's why I made two of them.
- Later on, Gaster tries to fix Sans' eye, but a power surge causes his head to blow up and nearly kills him. It's really disturbing so see him just barely hanging on.
- Not to mention, the only reason Gaster experimented on his eye was to try to fix his own. No excuse for helping the rest of monsterkind, just personal gain. That's messed up. There's also how casually he dismisses the damage immediately afterwards.
- In the comic "Can you overclock a hand reader" that has the boys exploring True Lab after Gaster's erased, the final panel implies the return of the tar monster that nearly killed them. The actual scary part, though, is that if you examine the comic closely, the "tar" is coming out of the gutter of the comic.
- The true nature of the tar monster; It's Gaster himself. Or more specifically, the part of him that had been so wrapped up in guilt that he psychologically tormented himself into becoming exactly the horrible person he felt like for so long. Because of how the void beyond the world works, he'd been there for every span of time simultaneously, and the part of him the brothers pull from the void isn't the man in full; it just happened to be the most "stable" part of him that hadn't also fully subsumed to his despair. The rest of him had conglomerated into a gigantic mass of bone and dark matter that sought only to make himself suffer for what he'd done and saw no other reproach.
Nightmare Fuel / Handplates