- R-D. There is nothing freakier than seeing what amounts to a clone of Dorothy(an emotionally subdued but otherwise nice girl), Slasher Smile and all, screaming maniacally at Roger just as she's about to put a bullet through him. If nothing else, that face...
- Also a 'face scare' is Beck's horrifying visage in the dark in his last appearance within the manga.
- Another is in the finale, with the eerily grinning and skeletal Big Venus.
- There's also the Megadeus that Schwartwald finds during Episode 4 if memory serves, the very creepy one that tries to "make friends" with Dorothy through unorthodox means. Nightmare fuel indeed.
- Made even worse in one episode of the second season: While being repaired, we see the Big O without its faceplate. It has the exact same head as the Megadeus from that episode. In other words, that thing is what the Big O looks like under all that armor.
- Roger asks as Schwartzvald is standing on it's shoulder, "Is that thing Big O's archetype?" It's surprisingly creepy for being a robot, the megadeus equivalent of a fast zombie.
- Alan Gabriel's demise. As he's about to finish off Roger, Big Duo suddenly stops responding. The wires hooking Alan to the machine suddenly wrap themselves around him, as well as all of the internal wires within Big Duo itself. Cue Schwarzwald appearing to chastise him and the words YE GUILTY flashing on the screen. Alan is then eaten alive by Big Duo's wires, which proceed to burst from the cockpit and spill out wildly as the Megadeus flies into space, so even if Alan were to somehow survive being suffocated by the wires, he would certainly die from the vacuum of space.
- Big Venus. Basically resembling Big O but with its colors inverted and sporting a large grin, it has the ability to alter and manipulate memories and reality itself.
- Heaven's Day's Bad Santa- yet another Mad Scientist (Dastun even labels him as such) wearing a suit much too big for his emaciated frame, and a face like a corpse. He's got no sense of personal space, and toggles between semi-lucid or ranting. After his one scene he disappears forever.
Nightmare Fuel / The Big O