Please don't list this on a work's page as a trope. Examples can go on the work's YMMV tab.
Nightmare Fuel: Alfred J. Kwak
A series about a charming little duck? How could this be filled with Nightmare Fuel? Well, first of all, though aimed at children "Alfred J. Kwak" had a lot of themes and hidden allusions to the adult world like Nazism, colonialism, epidemics, republicanism, Apartheid, doping,... When you're a kid all that stuff just goes over your head, but at the same time it can disturb you.
The opening sequence always featured a strange Big Lipped Alligator Moment, where Alfred is travelling by elephant. Suddenly he is lifted from the carriage by a huge black claw. In a brief flash moment you see a horrible skeletonlike creature who zaps him away! The worst part? It happened every time in the opening sequence, though the creature itself was never shown, nor explained in ANY of the episodes!
The very second episode is already traumatic. After getting acquainted with Alfred's parents, and seeing them raise a family only to be driven from their home, they and Alfred's baby brothers and sisters are all killed by a speeding car. The vehicle arrives, they look up to see the flash lights and then- wham!- they're simply gone. Alfred only managed to survive because he had wandered off by himself again.
Alfred and his friends visiting the Royal Castle on Alfred's birthday. Grabby the magpie steals the crown jewel during a tour, prompting Alfred to be accused of stealing it and then thrown into jail, where he spends a night alone in the castle, and is even told that his trial the next day will likely end with his own execution. Keep in mind that Alfred is just 1 year old at this point. The worst part is that his adoptive father, Henk, isn't informed about this and worries himself all that time.
Alfred and Dolf, trapped at the bottom a well somewhere in a lonely snowy landscape. To make matters worse, Krabnagel discovers them and tries to get at them so he can eat them.
While they are in the well, Dolf taunts Alfred for being raised by a mole, and says that in the Middle Ages, Alfred would've been banished out of town for being different. Alfred's imagination then runs wild, as he envisions himself in a medieval court with his personal teacher (with a truly awful Nightmare Face) sentencing him to be banished. The dream sequence goes further with Alfred being yelled at by the townsfolk and then literally thrown out behind the city walls. And there he stands, alone, with no friends at all.
In the sixth episode, Alfred and his school friends join in a triathlon. Since Dolf wants his buddy Hannes to win no matter what, he slips him some pills he lifted from the pharmacy to give him a tremendous energy boost. Unfortunately, as the pills were meant for elephants, they have some serious side-effects, and by the end, as Hannes stands triumphantly on the podium after winning the race, he suddenly begins to swell up to the size of an elephant, complete with his beak growing as long as an elephant's trunk. Hilarious to some, Body Horror to others.
Alfred going to the circus where he is confronted with a wild and dangerous beast. What kind of animal could be so dangerous in this animal universe that it needs to be locked away, you might ask? Well, its name is "The Human"! Some mind boggling Post Modernism!
Dolf taking over the country in a Nazi like dictatorship, causing Alfred and his friends to flee to a neighbouring country.
The Evil Genie of Darkness. Up until that point in the series, Alfred had only faced things like schoolyard bullies and foreign spies, making this guy an especially intimidating Outside-Context Villain thanks to his omnipotent powers and his tendency to eat whoever is foolish enough to release him from his bottle.
The hungry squid that tries to eat Alfred and on their way to the South Pole. His crazy eyes, deep voice, and Tentacle Rope don't help matters.
Alfred travelling to a country where black ducks are oppressed by white geese. Disturbing when you're a kid, especially disturbing when you get older and realize this is a reference to South Africa's apartheid policy, which at the time this series aired (1989), was still in effect.
The two-parter about two countries at war over their differing religions features a pretty intense scene of warfare, with infantry, tanks, and airplanes all going up against each other, and punctuated with a massive bomb exploding. Nobody dies onscreen, but the implications are clear that hundreds of animals lose their lives in the battle. Alfred even says so, though he didn't actually see someone either.
During a demonstration of a scale model of his fully-automated fishing boat, Hannibal uses it to catch one of the fishes in K. Rokodil's aquarium, who is then promptly processed and canned by the boat's inner workings. Eerily reminiscent of that scene in Who Framed Roger Rabbit with Judge Doom and the shoe.
During an expedition in the jungle, Alfred and the others are captured by some angry natives who decide to cook them into soup. Alfred is picked to go first and promptly lowered into a cauldron of boiling water for several minutes as he cries out in pain. When he is finally released, he's even turned completely red! Fortunately, he recovers not long after, but it's still disturbing to watch.