1. Creepy invincible enemies that follow you
That heading is pretty descriptive and easy to understand, but there are two such enemies that remain burned into my mind from my childhood and both are from NES games.
First, there was Phanto in Super Mario Bros. 2, a mask-shaped enemy that would come to life and chase you down as long as you were carrying the key it protected. Even if you went through a door, this thing was relentless and would follow you onto the next screen. The evil grin on Phanto's face scared me enough that I almost always took the warp to World 4 in order to avoid him in 1-3. You would think that when the original version, Doki Doki Panic, was remade into a Mario game for the United States, they would have made Phanto a bit less creepy. But no, it was actually the other way around; the original Phanto sprite lacked the evil grin and just looked sad and lonely. Nintendo thought American players weren't ready for the difficulty of the real Super Mario Bros. 2 (later released as The Lost Levels), but at least they thought us ready enough for a more horrific Phanto.
The other, was Baron von Blubba, which is apparently a "ghost skeleton beluga whale", but to me it was simply the restless spirit of some creature that wanted me dead for no other reason than that I was taking my time and enjoying the game. But to von Blubba, that meant taking too long to finish a level. The Baron is an impatient son of a blub who despises noobs taking too long in its game. And on that count, who can really blame him? I just wish he could've been a bit more polite about it. The fact that his coming was heralded by the most doom-filled music you've ever heard and coupled with the innate fear of running out of time didn't help either.
Honorable mention: the sun in Super Mario Bros. 3.
2. Various Parts of Super Mario 64
Overall, Super Mario 64 isn't a very scary game, yet from the very beginning I picked up on the eerily quiet atmosphere of Peach's castle, which was mysteriously devoid of any of Mushroom Kingdom's subjects except for an occasional Toad which materialized out of thin air. More disturbing, was Bowser's laugh which greeted me upon entering the castle; it was ominous, evil, and its source was unknown. Somehow Bowser was watching me and I didn't like it.
Then there was the level known as Big Boo's Haunt. This wasn't the first time that there were ghost levels in Mario games, but for me it was certainly the scariest. The ghosts weren't the scary part; in fact, once I encountered a Boo I found the level was less scary. What freaked me out was the "music", which was like an unnaturally low sound of howling wind. When you first enter the stage, you are outside the haunted mansion and the only music is the howling wind. It's desolate, creepy, and foreboding. Inside the mansion there's some doom-filled piano added to an unearthly droning sound which together set an atmosphere that is altogether more creepy than a Mario game ought to be.
If that wasn't enough, there is also a piano enemy, just for this level, which unexpectedly and loudly starts hopping towards you and chomping at you when you pass by it. Compared to all this, the underground carousel, which had its own creepy-in-context carnival music was a relaxing break from the dread-filled atmosphere of the mansion.
The last thing from Super Mario 64 that creeped me out and sent me seeking comfort from my mommy, is the endless staircase that lead up to the final boss. Throughout the castle there are doors with stars on them which only open if you have the required number of stars collected. In the case of the final star door which leads to Bowser, you need 70 stars, but if you have less the door still opens, leading to a staircase. It looks normal... but then it keeps going and going and going... forever. And once again, that wouldn't be so bad if it didn't have the mysterious music playing as you run hopelessly upward, driving home the point that something is seriously wrong. I didn't know how games were programmed or designed, all I knew was that stairs couldn't go on forever and that when I turned around I found I was only a few yards up the staircase, so something sinister was at work here. Suffice to say, I didn't go back in there till I had the required 70 stars.
Honorable mention: drowning.
3. Tourian in Metroid
|They want to hug you to death.|
Up until this point, all the areas in the game had been colorful and had pretty catchy, albeit slightly mysterious sounding music. Stepping into the gray and robotic-looking Tourian, with its comparatively dark and foreboding music was a bit of a shock. After that, it didn't take long before I encountered the metroids, which were, to me, unbeatable. Before I could say "screw attack", those metroids were on my head and draining my energy faster than a WoW addict drains a Mountain Dew. Like the endless stairs of Mario 64, something about Tourian just felt scary and wrong to me and I wanted no part in exploring it.
Honorable mention: encountering metroids in Metroid 2: Return of Samus (i.e. playing the game)
4. Missingno. in Pokemon Red/Blue
5. Adventuring in 3-D Body Adventure and 3-D Dinosaur Adventure
Both of these games were supposed to be educational and had a small variety of activities relating to their topics. I remember that you could view and explore 3D models of the human skeleton and organs or watch dinosaurs come horrifically to life out of a skeleton. Honestly, I have only a vague memory of what all the buttons correspond to on that 3-D Dinosaur Adventure screenshot, except in one case: the comet in the top right. That comet icon started the "Save the Dinosaurs" game, in which you had a limited time to find each dinosaur in a 3D environment. So basically, what it did was throw a helpless young boy into a maze with dinosaurs and told him he had only a few minutes before a comet all but destroyed the world. Sound like fun? It wasn't.
Inexplicably, the same company tapped into the exact same childhood fears in 3-D Body Adventure's "Emergency Game". When you start the game a voice tells you to "save the patient! It's up to you!" after which you are able to explore the hospital and select a patient to save, all while "HURRY DOCTOR, SAVE THE PATIENTS!" is displayed across the bottom of the screen. Sure. Alright, no pressure then.
But what scared me even more was when I discovered that I didn't have to do these operations and could explore the hospital, albeit still with a sense of urgency hanging over my head. In the video above, the player immediately turned and left the building but when I played I didn't realize that I could exit through that door and explored other rooms instead, getting more and more lost by the minute. Eventually, I found an exit and ended up outside the hospital. In the dark. Lost. And with dying patients. How do they expect to compensate me for all this trauma?!