As a Moments subpage, all spoilers are unmarked as per policy. You Have Been Warned.
Considering it's a show about all sorts of Eldritch Abomination creatures existing to scare the crap out of people and an actual inspiration for many nightmares in future shows and films, Nightmare Fuel is to be expected. Especially the more you know about the world of monsters.
- The anatomy of many of these monsters in this cartoon can frighten young viewers.
- Some of the monsters' scare tactics can be really creepy to younger viewers, such as Ickis transforming his body to giant size with blood-red eyes (pictured above) or most infamously, Oblina pulling out her internal organs.
- Throughout the series, there are a few references to the "Era of Disbelief", a period sometime in the forties when humans stopped believing in monsters which somehow nearly wiped out the latter species. If one tracks all the hints, one can work out that this period lasted from 1943-1945 — the period of World War II where the Allies managed to turn back the Axis Powers. Since the show later establishes that bad times for humans are good times for monsters, the implication is that the monsters gorged themselves on humanity's fear and horror during the Great Depression and the Holocaust, nearly went extinct as the world economy recovered and the Axis fell, and then recovered thanks to the Red Scare and the Cold War.
- This is shown literally in the episode "Where Have All the Monsters Gone?". It features monsters disappearing due to their failure to scare people. That's right, failing to scare people pretty much erases them from existence one body part at a time. And it nearly happens to Ickis, Oblina, and Krumm, who respectively lose their body, arms, and eyes. Also a Tear Jerker.
- The episode also confirms monsters exist because Your Mind Makes It Real. The Pool of Elders, the collective source and wellspring of all monsters explains to Ickis that monsters were born out of the fears of the human mind. It is that very fear that fuels the pool and continues to give existence to monsterkind. If the pool ever dries up, then it means a Cruel and Unusual Extinction for monsters as they'll begin to vanish from existence altogether. Monsters are literally forced to scare people just to survive.
- When the gang meets Krumm's uncle Grungy in "Monsters, Get Real", he's introduced stalking along behind them like a predator until he and Krumm recognize each other. Thing is, as the previous episode established and other episodes will hint at, Monstrous Cannibalism is perfectly alright in this world. Oblina herself even threatened to eat Ickis once. When you put the two together, you realize Grungy might have been stalking Ickis and Oblina in hopes of eating them!
- In "Smile and Say Oblina", Oblina gets hooked up with a metal device wired to her jaws with corkscrews and a timer on it. Fast forward to 2004, and we have a movie featuring a torture device that looks similar to that.
- In the case of Krumm's father Horvath, the method in which he lost his right eye as the infamous bullet in "The Shot Heard 'Round the World" is extremely terrifying. Imagine having one of your eyeballs loaded into a gun, this being the last thing it sees before the barrel clicks...
