The short vids with the sawtooth bear Radiohead advertised Kid A with. I was 7 and had no idea what a radio head is but that bear looked creepy af.

I had a great fear of social awkwardness growing up, so a shitton of rom coms were far more nerve wracking to me than any horror film, where at least the social expectations were clear (Stab Jack the Ripper with the hatpin) Like literally the scenes in The Worst Witch where she gets sent to the headmaster were scarier.

Oh, also, Cow and Chicken has always left me with an indescribable sense of unease.

Maybe this doesn't count because it's a horror/thriller and not for kids, but when I was like 9 I saw the horse scene from The Cell, and yeah it was really weird and liminal and scary in a way that I wasnt sure if I had dreamed or imagined it. But the real story is that this scene and maybe that whole film is apparently an SCP, because it turns out fucking everyone who knows about this movie first encountered it in the exact same way.

Indiana Jones and the Infernal Machine- The big roaring scary ice monster boss beneath the (really quite beautiful) abandoned temple in Khazakstan.

Jedi Outcast: The dark crystal caves full of chompy bug things and slave corpses in the Imperial prison mine, where you need to use night vision but the batteries are limited and did I get turned around in that last tunnel oh god the clock is ticking oh fuck I can hear them scuttling

In both cases young me was too spooked and had to call in reinforcements (my dad) to get me through those sections

i was just a perpetually terrified child, but it really started when i started trying to read my elementary school library and started with the nonfiction, and in the 000s (i think the 040's) you find all the books on werewolves and curses and vampires and stuff. scared me so bad as a little 5 year old

As I remember it, the concept of the pink ink drinker from one of Dr. Seuss's books scared me a lot. I thought about it drinking all the pink ink and then it being gone forever. A sort of baby's first understanding of the march of entropy.

The zombies in half-life scared the ever loving hell out of me. I used to noclip through areas if the zombies were there and physically closed the game if I ever got caught by them.