Several people are terrified by Boos. It pretty much all boils down to the fact that they only chase you when you're not looking. It only leaves the door open to Fridge Horror.
This series introduced the concept of spikes = instant death in video games. Good thing everything causes Mario to go into Death Throws. Doesn't stop some kids from being scared by the thought of falling and getting impaled on spikes, and the resultant saturation of spikes in video games as a whole causes nightmare fuel filled scenes in video games where they DO impale you.
Super Mario Bros.
The first Super Mario Bros. gave us the Minus World, a world no man is intended to go to and has no escape, unless you count drowning to death or the reset button as a method of escape.
If you let a Hammer Brother stay onscreen too long without killing him, he will chase Mario.
The castles in the first Super Mario Bros. game for the NES are really, really terrifying. There's just something about them; the lifelessblack background, the pointy-looking lava that doesn't move, the revolving sticks of fire, the fireballs that come as you approach Bowser's lair, Bowser himself (especially later on when he learns how to throw hammers)... and that music. THAT MUSIC. Some of the castle levels are mazes that will repeat endlessly until TIME RUNS OUTAND YOU DIE. (or until you find the correct path)
The famous cave music probably creeped out more than a few kids.
Super Mario Bros.: The Lost Levels (Japanese Super Mario Bros. 2)
The firebar in C-4 that practically requires you to take a hit. If you're Small Mario, it's almost impossible to pass.
8-4 and D-4 both have two Bowsers in one castle (one of them is fake).
Super Mario Bros. 2 (USA)
The Hawkmouth in Super Mario Bros. 2 (the one that acts as an end of level gate) scared the crap out of some in the end of World 7-2 when it flew off the wall and tried to chase them!
And then you get past the door to confront Wart — and the music changes to this creepy, disturbing horror/techno mix that just messes with your concentration while you have to catch vegetables in midair and throw them into Wart's open mouth (as opposed to the other bosses where you just had to hit them with weapons).
Phanto. Creepy pumpkin masks that guard keys; when you pick up a key, they come to live and move really fast and chase you.
In remakes, World 1-3 in particular has a chamber with a key, a squad of phantos, and a giant Phanto face in the background. When you pick up the key, the background Phanto face's eyes light up red.
At some point Mario swims through a lava-like substance in 8-Battleship... Just a hint: The lake is not NOT lava. If you could not figure it, it is BLOOD. Yes, you swim through a lake of blood.
The Angry Sun made some too scared to play past World 2.
Some were also afraid of the Podoboos in the World 1 mini-fortress.
Chain Chomps debut in this game, and there's a quirk to their behavior that not many know about. If it pulls on its chain 50 times or if the timer hits 160 seconds, it escapes.
There were also some terrified by the Hot Foot in the first fortress of World 4.
The laser-shooting Bowser statues in his castle.
The first fortress in World 7, since the entire place is empty. No enemies whatsoever (barring the boss). Even worse is that one can see where the enemies would be, giving the feel that it was just suddenly abandoned.
In the Super Mario All-Stars remake of Super Mario Bros. 3, World 5's blue mini-fortress has both a lava floor and a ceiling. It's even more unsettling considering that in SMB 3, lava isn't merely a harmless curtain for the top of a Bottomless Pit; rather, touching it kills you instantly, even if you're Super Mario. Or powered-up with the invincibility star for that matter.
Boss Bass from Super Mario Bros. 3 and Super Mario 64. Super Mario 3's Boss Bass in particular has this habit of jumping right out of the water, snatching you right off the surface and swallowing you whole in one gulp.
And what makes it even more nerve-racking that by swallowing you whole in one gulp, means that no matter what power-up form you're in, being swallowed and gulped is an instant death regardless.
SMB3 can be corrupted too, as ProtonJon found out. The video is called "Super Mario Bros. 3: Nightmare Edition."
Super Mario World
In the final battle, Bowser is seated in a hovercraft which is painted like a clown's face. After Bowser is hit a number of times, he flies forward, so that the screen zooms in on the hovercraft. Push the pause button at the right time, and there is a screen full of clown face.
Then said Clown-faced hovercraft in its final phase with its eyes being butch and angry while still smiling as small veins pop out at the side of its head, all the while trying to pound and crush you.
If that's not bad enough, the epilogues of Morton, Ludwig, Roy and Wendy imply that you killed them. On the other hand, they did return in later games, so the descriptions were probably added for shock value.
Lemmy and Wendy's deaths are even worse in the GBA port of the game. Apparently someone thought it was a good idea to add a sound effect that sounds like a shriek of agony to them (along with Iggy and Larry).
The big green bubbles in the Vanilla Ghost House freaked many out a bit. They were large, invincible, and always got in the way, and if even two closed in on you, you were screwed.
The way secret keyholes grow so huge and then swallow up Mario is just plain freaky. The accompanying music only makes this worse. The GBA port makes it even worse, because the music in that one has a louder bass line at the end that acts as sort of a Last Note Nightmare.
The Big Boos from Super Mario World gave some fright as a kid, but the Monty Moles just continuously pop out and attack.
The graphics in Super Mario World. Most of the time, they were gorgeous. But many of the enemy sprites were just wrong. The weird, hunched-over shell-less Koopas, the odd posing and so-smooth-it's-creepy animation of the Charging Chuck, the weird stick legs on the Koopa Kids... not to mention the fact the player's death sprite, it looks like Mario is bleeding from his eyes! Accompanied by a Scare Chord, no less!
Those creepy looking Bowser statues in Bowser's Castle if you took one of the rooms, only to encounter a golden, animated one.
Lava appears in some athletic/overworld levels. Except, due to palette differences, it's colored brown. Functions exactly the same, except, well, what is it? Mud? Melted piece of the ground? So bacteria-filled and acidic that bubbles come out?
It's molten chocolate. That the stuff is only encountered on Chocolate Island is something of a giveaway.
Big Boo in Super Mario World has a placeholder sprite for use before the final sprite is loaded. If seen at all, it's likely for a split second. However, it's an empty, soulless emotionless face that for some falls right into the Uncanny Valley.
Which technically, just happens to be the same face Big Boo makes when facing it, just without being covered by the sprite's arms.
Sunken Ghost Ship, specifically, the loooooong drop that occurs at the end of the level. What makes it freaky is that the background is pitch black, meaning you have no frame of reference aside from the coins that you drop past. Then suddenly, after the super long drop, you either land on a small platform with the goal orb, or you land in the nearby water and have to jump out before the mines above fall onto you. The fact that this level reuses the dissonant, creepy music from the various Ghost Houses doesn't help. Finally, when you complete the level and uncover Bowser's domain, there is no music when you regain control on the world map. The lack of music also happens on subsequent clears of the stage.
Super Mario 64
The Mad Piano in Big Boo's Haunt, when invoked, it grows teeth and tries to eat you (as seen above). To make it worse, it sounds like someone angrily banging their fists on the piano keys. Much of Mario-related trauma has come from that enemy alone. And to add insult to injury, one of the red coins is located behind it.
The Big Boo fights and the music were also something else to be scared of, not to mention the creepy calliope music from the carousel.
There's that one dark room where the bridge you walk on crumbles, and if you fall into the darkness, you startlingly land in the underground passageway with the carousel music.
"Ghosts...don't...DIE! Can you get out of here...alive?"
The entry to Lethal Lava Land (remember, that flaming face painting◊?) was frightening enough to scare you out of the room. Worse yet, it is the same face that shows when you lose a life from running out of life or by hazards, in other words Bowser attempts to scare you.
Mr. I. No matter where you go or how fast you run, he's always WATCHING YOU.
What happened when you ran into a door when you didn't have enough stars to open it. Bowser cruelly laughs at your misfortune.
Unagi.◊ It was a huge eel with a freaky face, topped with the fact that he doesn't look quite that big at first.
The DS◊ version manages to be even scarier due to it's eyes being smaller and it's teeth being sharper and longer.
Bowser himself. It's just the way his model looks, always with that evil look on his face, and if anything, the polygon look just made him scarier.
He's especially frightening in the final battle, due to his green glow, his three varieties of fire breath attack, his seismic stomps, the fact that one bomb isn't enough to end him this time, and especially the music.
That GIANT FREAKIN' FREIGHT TRAIN-MONSTER that is the Chain Chomp◊. Shigeru Miyamoto designed Chain Chomps based on his own fears of being bitten by dogs. Thanks, Miyamoto, for making sure your own nightmares fuel other people's nightmares.
Super Mario 64 DS manages to make Big Boo's Haunt even scarier by adding the area where you get the key to unlock Luigi. You jump in as Mario and arrive at an area that seems like a rather simple Lost Woods like level, where a wrong door will take you to the beginning of the level. Wouldn't be too bad if it wasn't for the absurdly frightening laughter King Boo keeps dishing out as you run through the level...
The only truly scary parts would have to be Eyerok, the Shifting Sand Land boss. The two big-ass rock hands with eyes on the palms. The ones that try to push you off the slender platform and into a pitch black emptiness.
Dorrie, the creature from Hazy Maze Cave. The big blue dinosaur with the red slit mouth and tiny eyes that a nearby sign claims will eat you.He doesn't, but still. Thankfully turned into Nightmare Retardant in Super Mario 64 DS with the addition of swim goggles, as well as making his face more Yoshi-like.
Mario's drowning animation. Mario desperately struggles while seemingly making failed attempts to gasp for air in blind panic and agony, with the game fading out as Mario's corpse is going limp. The poison gas death (the area mentioned above) is no better, with Mario grabbing for his throat, then falling on the floor with the screen fading out as he lies twitching (apparently still alive) in his final moments on the floor. The toxic area was really the worst in that, as anytime you are breathing it Mario would cough and slowly choke as if struggling for air.
Playing with Gameshark in Mario 64 can get you very disturbing results. This video, one of the many that refers to Gamesharking in Mario 64, leads the watcher to the ultimate nightmare, especially as Mario enters the castle lobby.
The painful cry Mario did whenever he got hurt in Mario 64.
In Super Mario 64 DS, if you play as Luigi and turn invisible in a Mirror room on the third floor, you can go through the door that is supposedly the reflection of the entrance door. Going in there, you find yourself in a white abyss with nothing but you, the door, and a power star.
The underground/water town in Wet Dry World, along with the background to the level (a city of flat-roofed buildings). Completely deserted excluding a lone Bob-omb. What exactly happened there?
Justified slightly in that the background looks like an ancient city, so the town could have been empty since ancient times. But considering that it probably flooded every five minutes, it's no surprise it went empty. Perhaps some evil person got his hands on the water crystals...
This one is a long shot, but the main HUB itself could be creepy if you think about it. You're in a big castle/mansion.....all alone....except for the Toads.
When you get the Power Star from atop Bowser's submarine, the sub disappears from Dire Dire Docks for stars 2-6. And that Bowser door opened underwater... becoming a big black hole that SUCKED YOU IN if you got near it.
The secret under the moat. It takes place in a gigantic room that is 95% void, with the level itself taking place along the edge.
The Game Over screen. Mario's face, contorted in pain and exhaustion, against a dark red backdrop, with a warped excerpt from the Main Theme playing in the background, was rather overstimulating for some younger players.
Mario dying from electrocution. Most deaths involve Mario doing something even the slightest bit comical, such as trying to get back up and then passing out or struggling against what killed him, or being squashed flat. When Mario is electrocuted he goes limp and flops over. The end. That's it. With all the other deaths, gruesome as they are, involving some sort of drama, seeing Mario just...fall...is more than a bit disturbing.
The whirlpool of Dire Dire Docks. It sucks you in and instantly kills you (and you're required to get close to it in order to get a Power Star). For that matter, swimming alongside those sharks and that huge manta ray can become very unsettling.
Super Mario Sunshine
Super Mario Sunshine, an otherwise rather bright game, features a level where you have to go underwater (thus, making it a Timed Mission), and clean the teeth of a giant eel; complete with poisonous bubbles and a whirlpool that threatens to suck you in.
The Gooper Blooper battles from Super Mario Sunshine. Mario is fighting a giant squid who uses his tentacles and ink that summons slimy enemies to attack. The method of defeating him is to jump on each of his tentacles and graphically pull them off one by one; after doing so, the pulled tentacle will wriggle wildly before disappearing.
Phantamanta is a pretty frightening boss, and a pain to beat as well. It's a borderline Eldritch Abomination that can move over ANY surface like some kind of shadow and leaves a trail electric goo, and when you spray it, it splits up, spray them and they split up, spray THEM and they split up! Then, once you got it into its SIXTY-FOUR parts, they all turn red and charge at you like mad!
The Boos in Hotel Delfino look rather demented, with glazed over eyes and tongues hanging out more than usual. They even look outright stoned.
New Super Mario Bros.
In New Super Mario Bros., Bowser falls into lava in the first world. Not much different from what happened at the end of every single castle in the original Super Mario Bros... until the game proceeds to show him desperately flailing in the lava, yelling in agony, and emerging with all of his flesh melted off. Totally unexpected and freaky as all get-out.
Mario's next line, immediately after the whole debacle? "That's-a so nice!"
Later on in the game, it turns out that he's still alive and continues to live on as a skeleton. Which meant he actually got to feel his flesh burn off. Wow, Nintendo.
In the final level, Bowser Jr. uses a magic cauldron to restore his father to normal.
Super Mario Galaxy
The giant caterpillar in the Gusty Garden Galaxy of Super Mario Galaxy. The way it's almost realistic in appearance in a game with an intensely cartoony art style creates an effect similar to the Uncanny Valley, and it makes some genuinely disconcerting high-pitched noises. The enormous nose and buck teeth do little to diminish this.
When Mario's hand rises up when he sinks in sand or toxic waste, all while hearing him drown.
When Mario touches dark matter, he slowly disintegrates, and his life bar isn't empty until AFTER Mario is completely gone. He feels the whole thing!
And then there's dying of electrocution, which leaves only a skeleton.
The Gringills in the Beach Bowl Galaxy. The giant ones with googly eyes and teeth almost as long as their head.
In a little more detail; you're swimming through a beautiful galaxy full of clear water and cute penguins, not many enemies at least not at first, but then you come to a dead end and a giant Gringill comes EXPLODING out of the darkness and flails about with another little one above it.
The hovering, screeching Cluckbooms. There is just something vaguely disturbing about them...
The Bonefin Galaxy, home to the giant skeletal shark known as Kingfin.
The giant jellyfish. Sure, there were only two, but each one was in an rather off-putting location: the first in the Bigmouth Galaxy, where more and more ghosts kept popping out of nowhere underwater, and the second in the Deep Dark Galaxy, where you HAD to swim RIGHT PAST IT because it took up most of a certain passage. (Oh, and both galaxies had some of the most ominous-sounding music in the game.)
Also in the Deep Dark Galaxy is a planet accessible by a cannon, which is basically a tiny version of the first planet in Gateway Galaxy. It's kind of odd in the first place to come across something like this, but if you jump on a nearby screw and spin around, the planet will deflate like a giant beach ball. It even rewards you for doing this with coins!
Between them, Mario and Bowser wind up destroying the universe.
The music that plays when you wake up the Dino Pirahna is very unsettling, as is the fact that you are on a small planet with the possibility of being plowed into by a giant, blind beast. The Dino Pirahna itself is no better, especially when you get it angry. And when you defeat it, the idea of having just killed a baby doesn't sit right either.
Also, when Dino Piranha dies, its red skin turns a pale purple. Anyone who knows anything about babies or humans in general knows that skin turning blue is not supposed to happen.
In one of the later areas, you come across FIERY Dino Piranha. The guy was freaky enough the first time around, but, ON FIRE?
Luigi's deaths in SMG. Poor Luigi sobs hysterically as he falls to his death.
Even worse is when he falls in quicksand or the swamp goo. His scream sounds distinctly like "Help help can't swim!"
Also, right before Bouldergeist explodes, his uvula pulsates, his head shrinks, and his eyes triple in size... and he explodes...
The Lumas' cycle of gorging themselves, and then committing suicide by exploding into a new celestial object. They are eventually being reborn somehow, but these guys are happy that they are exploding.
Outside of the small planet the boss Kingfin resides in, a random Toad Brigade ship. This doesn't seem scary at first, but then you realize the ship is empty and the toads are nowhere to be found, and a giant, Jaws-size skeleton fish down there has teeth that look sharp enough to rend flesh. Uh oh.
Super Mario Galaxy 2
Cosmic clones in Super Mario Galaxy 2. The ones in the previous game were simple Mario and Luigi clones that served as racing opponents. In this game, they follow your every action with a delay of a second or two. If one catches up to you or you bump into one, it hurts. You can't stop for even a quick breather or you'll get hit. And they keep coming. More and more of them get spawned every few seconds, leading to a seemingly endless chain of them. Even the nearby signs are afraid of what they can do. And worst of all, their corruption extends as far as Luigi's Purple Coins...
They mimic their movements perfectly, a few seconds after they do. You touch someone on the shoulder, they touch them seconds later. You pick something up, they mime picking it up themselves. And if you stand still, they collide with you, exploding into dark energy at point-blank range. And until you, or possibly somebody else the comet is focusing on, finishes an arbitrary task, they spawn forever. Following you everywhere. And when you think about it, aren't the other comets also Fridge Horror? Just think of what happens when, say, the Red Comet gives one arbitrary person a time limit to do one task before dying.
In several late levels, giant lava monsters suddenly rise up from out of nowhere and engulf your platform in their mouths. The last one is particularly memorable.
In one galaxy, a group of penguins are out swimming, watched over by a couple of larger penguins. To get the non-secret star in that stage, you must hit a switch that causes the entire area to freeze solid. It's not just the surface; you can see them under the ice, frozen in midstroke.
In the Shiverburn Galaxy, if you change the camera to first-person mode and look toward the cliffs above you, there seems to be three mysterious shadowy figures on the cliff, watching you, and following you. You can read about it here.
They're supposed to be trees. It doesn't help though, because they don't look at all like trees. And they have glowing eyes. Brrr.
The file names? BeyondHellValleySky is where they reside, and HellValleySkyTree is the names; the ominousness of the trees were enough, but those names make them worse.
The swirling spirits in the background in the ghost levels.
Magmaarghs (a much larger version of Blarggs from Super Mario World). They're huge, hideous creatures made of lava who look incredibly deranged, with strange eyes and huge mouths, and when they try to collapse into Mario or Luigi, they make a very disturbing roar until they lose their form in the lava.
Bowser himself, as he's immensely powerful and gigantic in this game. He nearly devours Rosalina and her starship, and creates a black hole that he's in complete control of.
Super Mario 3D Land
An Easter Egg: In the yard at the end of any ghost house, waiting long enough causes a ghostly figure to appear in the background just behind the fence and will vanish after a few seconds. This figure doesn't actually do anything and cannot be interacted with, but what makes it creepy is that the thing resembles the Shiverburn Galaxy figures. They're not trees. They're still watching. And they're getting closer.
Even worse, it could be Slenderman, in a frigging Mario game. And as a bonus, it opens its mouth before disappearing, as if trying to scream at you... brrr.
The connection between the spirit and the [HellValleySkyTree]... there's also a UFO visible if you wait a minute at 1-3. What other freaky stuff has Nintendo put in these games? Are they... are they trying a secret subplot told through weird Easter eggs?
Come to think of it, that UFO...we've seen a UFO like that before. Specifically, one that helped Bowser to airlift Peach's Castle in the first Galaxy game... Yes, others appear in later levels, but that first one that helped kick everything off—Bowser did not just happen across it on his own...
The cosmic clones. They mimic Mario's quotes, but in a higher pitch with added distortion. When they say "Let's-a go!", it sounds like they're saying "Time to chow!". Yikes.
New Super Mario Bros. 2
The Boohemoth, a massive Boo enemy, is bigger, chubbier, and his eyes don't look at all like the charming dot eyes that normal Boos have, but more into the Uncanny Valley. Although he only shows up in two Ghost Houses, he'll appear without warning with a Scare Chord and chase you. He too stops and hides his face when Mario or Luigi looks at him, but every so often he'll peek and approach anyway. Thankfully, he only appears in two levels.
In World 6-Castle and World Star-Castle, Mario has to make his way across a lava-filled platforming level. The kicker? He has to avoid the Koopalings' special petrifying gaze. If he's not hiding behind a wall, one wrong step and he'll most likely freeze, and fall into lava.
Super Mario 3D World
As cited from a Miiverse post, the Shiverburn figures are back. They can be seen through a reflection on a Clear Pipe Cannon on the last main level, The Great Tower of Bowser Land.
The post? "Anyone remember those mysterious faces on the top of the cliffs in SMG2? Or the mysterious face in the ghost house in SM3DL? Look closely at the reflection in this photo. Tell me what you see."
It seems Nintendo is slowly trying to implement their own darker version of Where's Waldo?.
The way the enemies die is actually kind of creepy. Unlike the NES Mario games, where enemies generally flip upside-down and fall off the screen when you jump on them, here they lay on the ground, flattened and dead for a few seconds, before flopping off the screen. It gets worse with the Koopa Troopa analogues, which explode when they die.
The "Daisy"s at the ends of Worlds 1 through 3 of Super Mario Landthat are actually monsters can make the player jump a bit.
There are bonus rooms with Spikes of Doom. Coupled with the quiet bonus room music, Mario accidentally jumping onto the spikes and dying is pretty frightening.
The U.S. commercial for Super Mario Land 2: 6 Golden Coins. To some it may be Narm but before Wario was the portrayed as the greedy character he is today, in the U.S. the American media in the early years of after his debut portrayed him in a way that made most young gamers rather afraid of him, The commercials for Virtual Boy Wario Land and Wario Blast didn't help matters.
The Thwomps from Bowser's Castle in Mario Kart 64; it's that disturbing Evil Laugh. The green one in the cell is scarier for some reason. Luckily, they aren't scary in the Wii version's remake.
Mario Teaches Typing 2, like Mario 64, featured the floating disembodied head of Mario. Unlike the Mario 64 version, this one goes back and forth between cracking jokes and being amusing, to being just plain unsettling at times.
The GBA puzzle game Mario vs. Donkey Kong features a relatively realistic 3D rendering of Mario facing off against cartoony Thwomps and Shy Guys, and is brought up at this point in the page due to its Galaxy-like series of disturbing death animations. The default animation (for example, stepping on spikes or touching a Shy Guy from the side) has Mario tilt briefly before he falls face-first into the floor (or spikes!) and stops moving. Then there's the specialty animations for dying to a fiery or electrical attack, which don't pull any punches about how terrifyingly painful it must be for poor Mario.
There are three different "death" tracks in the game's BGM. While the first two apply for "standard" deaths (the second is used for getting burnt by lava), the third is used for the most horrifyingly painful and gruesome (for Mario standards, that is) death animations, such as getting squished by a Thwomp, falling from a high place (with Mario falling on his head as a result) and, last but not least, getting electrocuted to death. In fact, you can tell the various deaths apart by listening to the different pitches of Mario's variants of his classic "Mamma mia!". The first is "standard", the second is "exhausted", and the third is "a mixture of pain and horror".
Mario Tennis was the game that debuted Waluigi. In his debut, Waluigi, not only was pretty creepy looking, but made extremely weird noses all of the time, almost like a psychopath groaning in pain or delight. Whenever he scored, his celebration would have him making his eyes glow and flash purple, all while bearing the demented grin frozen into his face. The glowing eyes, to this day, remain unexplained.
In Mario Power Tennis, when Yoshi wins a trophy, there's an animation in which Luigi brings it to him. Things go awry, and in the end Yoshi has swallowed Luigi. He doesn't get spit out. There isn't even an egg. He never escapes.
Another one involving Luigi, Luigi delivers a trophy to Shy Guy. While walking toward Luigi, Shy Guy suddenly trips and his mask falls off. Only Luigi sees what's under his mask, and he is terrified. What is under a Shy Guy's mask!?
Actually, Luigi already knew before then. In Luigi's Mansion you can remove the masks from Shy Guy ghosts revealing their heads to be completely hollow
The end of Mario is Missing!, when Bowser is defeated, may scare some young children. You don't fight him, he comes out of nowhere and is shot out of a cannon, innocent enough. It's cartoony. Then he falls into the ice, freezes up, is covered in snow, then shatters.
Also one of the versions you have to rescue King Kong. The image you get of him is his fist wrapped around the entire Empire State Building. Something that big is too terrifying for words.
Also, one of Peach's screams when she is electrocuted sounds like a realistic interpretation (i.e. screaming bloody murder) of feeling that type of excruciating pain in contrast to some of the other screams. Think about how she and the others feel in a more realistic way after that.
The Game Over theme from Super Mario Kart. What's scary is that if you lose all your lives, the screen darkens, your character vanishes, then "GAME OVER" drops in ghostly-like letters, with that nightmarish music playing in the background.
In Super Mario RPG, there's a room in the Sunken Ship with a Mario clone that seems pretty harmless, like any other NPC. Except that said Mario clone TURNS INTO A GREAPER out of nowhere, and you enter battle.
When you initially arrive at Seaside Town in Super Mario RPG, there is definitely something off about the place. The townspeople all look identical, and display disturbing behavior, like stopping mid-sentence to quietly converse with each other, and watching you sleep. It eventually turns out that a Smithy Gang member named Yaridovich took over and impersonated the entire town.
Smithy, himself. Imagine a cyborg-bearded-giant-king-mechanical being, with More teeth than the Osmond Family, and a couple of replaceable heads, each just as creepy as the original.
The factory's basement where the final battle takes place, the floor is made of nothing but several Smithy's heads, and some particularly interesting ones seems to be looking at the player. It would be harder to beat him if those eyes were glowing...
This was the first Mario game to feature apparent actual death of NPCs, mainly Toads.
Cackletta possesses Bowser and turns him into a mutant hybrid of the two. And to fight her, you have to go inside Bowser and fight Cackletta in the form of some spirit/gas thing and attack her heart.
Joke's End. It's the Slippy-Slidey Ice World (minus Frictionless Ice) of the game. In contrast to the smiling faces littered all over the other areas, Joke's End has expressions of despair littered all over. Frozen. It wouldn't be so bad if this weren't the music.
The statues found in Joke's End depict great suffering, with hands placed over their ears and tears streaming down their cheeks. It's almost like the place is the hell of the Beanbean Kingdom. And it is. The theme of the Beanbean Kingdom is laughter, and Joke's End is the final resting place for cruddy jokes. The miserable-looking statues covering their ears may be meant to represent just how horrible a bad joke can be to the people of Beanbean.
Many of the places that Cackletta involves herself with? Yeah, they become this.
The Mario Bros.' first visit to the Beanbean Castle Town. The houses and buildings are all wrecked and innocent civilians lie on the ground like they're on the verge of death. The music makes it feel like you're walking in a graveyard.
It gets worse. You end the game with the town in this state. Yeah after having a nice town for a good portion of the game, it's reduced to this sorry state by Bowletta during the endgame.
Partners in Time
The Shroobs. They are basically evil mushrooms that invade the Mushroom Kingdom because their home planet is a barren wasteland. They reduce the Mushroom Kingdom to rubble, and take it over. Then, they begin taking the population and turning them into FUEL FOR THEIR UFOS!?WHAT THE HELL NINTENDO!?!
The Elder Princess Shroob: she is a giant mutant with numerous tentacles for legs and for arms, and a hideous face. To make it worse, she attacks by even shooting down her own men... Also, her battle music is a strike in "Soundtrack Dissonance".
Toadwood Forest and the Vim Factory. The Shroobs are using the Toads' LIFEFORCE to power their spaceships. Also, after defeating the Swiggler, you can still find Toads strapped to the trees!
When Peach first goes on her trip, she is accompanied by two Toad attendants, Toadiko and Toadbert. By the time you encounter Toadiko, she is already near-lifeless because the Shroobs were sucking her vim away. Then, she is found out and turned into a Shroob mushroom, presumably dying (If she doesn't, it's even worse). Toadbert traumatically loses his memory for most of the game, and is promptly turned into a Shroob mushroom as soon as he recovers it. In both cases, this is softened by the fact that they, like all of the Shroobs' victims, recover (Toadbert's even returns as comic relief in the third game), but still, this is some hardcore stuff, especially considering we don't even know how long they've been like this.
Inside Yoob, you can see him wince in pain when the Babies use the hammer or the Baby Drill. The latter is especially wince-worthy if you consider that Yoob just had something drilling into his flesh and is moving underneath it.
Bowser's Inside Story
Mario & Luigi: Bowser's Inside Story. Much of the game takes place inside Bowser's body. Which is strangely maze-like and platformer-esque. You have to manipulate Bowser's organs at times to get Bowser moving or affect him. The idea that Bowser has these characters running around inside him affecting his bodily functions and messing with his insides is very grotesque. Plus, some of the enemies are odd, virus-like versions of regular enemies such as Goombas. Enemies that Bowser inhales can damage him internally by attacking his body! And all the Toads are infected with a disease that makes them inflate in size and roll around uncontrollably!
Giant Battles always start with the soon-to-be-fought Humongous Mechacrushing Bowser.
The final boss fight. Fawful has transformed himself into some really freaky spider-like/bug-like thing, and is inside Bowser's body, transforming his stomach into something mutated looking. And his face... It's really disturbing to think about.
One of his attack is very creepy, to the point you would hope to never see it when you play... BUT YOU WILL!
The song played in Fawful's Castle from Bowser's Inside Story.
The Dark Star in general is creepy — it is literally an embodiment of evil that can absorb other beings to use as a source of power, as it does to Fawful! Then he turns into an evil version of Bowser sporting a mohawk! Oh yeah... IT SHRIEKS.
The cutscene where the Dark Star chokes the Mario Bros. with its dark energy.
The Final Boss. Bowser attempts to wish Mario and Luigi away with the Dream Stone, but when that fails he settles on absorbing its fragments to turn into a Reality Warper capable of doing anything he desires. Just because the Dream Stone embodies good dreams doesn't mean those good dreams are benevolent....
The last segment of Neo Bowser Castle. Things start off when the Mario Bros. find the source of all the nightmare veins. Then Mario enters Bowser's dream, which is about as disturbing as you'd expect a dream of the Koopa King to be.Themusic really sells the whole thing.
Specter Inspector. Once one player successfully finds three of the five creatures, the room lights up and the winner stands with all five as they all wave happily at the player. And then the camera zooms back to show that they're all trapped inside a painting in a dark room, as ghosts leer at it. Remember, this is the winner...
To say nothing of Bowser's Big Blast from Mario Party 2/4, and Cut From The Team from Mario Party 8. The tension alone makes the heart race in fear. Who will die first? Will it be you, or your friends? You're at the mercy of Lady Luck as you slowly step forward and meet destiny...
The entire Mario Party series is accidental nightmare fuel, especially the first ones. Any of the minigames involving Boos eating the losers was creepy.
When you think too much about it, hell yeah. There was Ghost Guess in the first MP where you had to guess which was the leader of a pack of Boos (a dozen or so) circling you. The game gives you the tip: the first one to start their dances is the leader. But then again, it's pretty hard to figure out which of them does it. And when you pick the wrong one... All the Boos converge on you and take you to God-knows-where. As soon as they're gone, so are you. Shudder.
And then there's Pedal Power, one of the games that used the infamous Scrappy Mechanic of "spin your Control Stick around like there's no tomorrow". You have to pedal a stationary bike to light up a lamp behind you before the Boo gets you.
Running of the Bulb is a very good example. Four characters have to protect a lightbulb as they run down to the end of a dark, boo infested hallway while being chased by one large, rather frightening looking boo. Letting this particular boo catch you means you dissappear in a simmilar fassion to Ghost Guess. Going even further, the lesser boos are apparently capable of possession. It's pretty creepy having Mario characters slowly chase you zombie-style while glowing with a ghostly blue aura. And if you're the one possessed, all you can do is hope that another character will take the time to knock you back to your senses, and pray that the boo controlling you doesn't decide you to just go ahead and feed you to the big one.
Speaking of the original, some find the Options House terrifying! Mainly because of the freaky background music, but also the process that you go through to delete your save data feels like you're activating a nuclear missile!
Super Princess Peach
In Bowser's Villa, there are a couple of segments that contain several faceless Peach statues and a HUMONGOUS Thwomp that takes up the entire background. Before it opens its eyes to scan the area, you have to copy the poses the statues are in. If you fail to do so, you'll be sucked into his gaping mouth. Of course, you'll only be sent to the beginning of the segment, but still...
And then there's the wall of Langolier-like Boos.
Perry devours baddies to recover the Vibe Gauge. If there are no enemies nearby, one can stand still for a few seconds, cuing an idle animation where Perry latches onto Peach's head, to her vocal displeasure, regaining Vibe Gauge that way.
The Mad Boos and Mad Big Boos, which look positively Ax-Crazy.
In Bowser's Villa, there are several segments where you constantly need to avoid a pair of mechanical claw-like things flying in from the sides. Get caught, and you're treated to Peach being helplessly trapped in them while they begin a countdown to explode.And there's nothing you can do if you get caught.
Super Mario Bros. The Movie
Daniella and Daisy's kidnappings are played to scary effect, and as far as the residents of Brooklyn knew, they and the other girls were missing and probably dead.
Koopa coming on to Daisy. With his face and tongue getting... less human. (Early drafts suggest he was attempting to rape her.)
Koopa snapping and attacking Luigi after politely asking them for the rock.
With a bit of Fridge Logic, the brothers dissolving between dimensions. Mario was conscious of the fact that he disintegrated.
Koopa's Transformation Ray, especially in the deleted scene where a guy gets devolved into slime.
According to Mojo Nixon, who played Toad, Dennis Hopper's performance as Koopa legitimately scared him during the scene where Toad de-evolves. Toad freaking out as he's strapped into the chair wasn't acting.
The Snifits, due to those weird noises they were constantly making.
Lena stabbing Yoshi.
Goomba!Toad getting set on fire.
Lena shoving a guy out of the way by grabbing his face, then getting electrocuted when she dives for the meteorite piece seconds later.
"Love 'Em and Leave 'Em": Queen Rotunda, an Expy of the Queen of Hearts, ordering the Marios to be executed, yelling "Off with their heads!". Then, Mario tries to intervene, causing the queen to ask why he still has his head!
The Koopas revealing their trap in "Send in the Clown". Several Thwomps block the exits as the cavepeople and the Marios try to escape before they are forced into a cage where some terrifying hungry dinosaurs await them.
"Ghosts R Us", where Yoshi must save Mario, Luigi, Princess and later Oogtar from a haunted house. Their captor, Wizardheimer, isn't exactly Mr. Nice Guy. Probably because they keep screwing up his name.
Koopa threatening to feed Oogtar to a dinosaur in "The Night Before Cave Christmas".
"King Scoopa Koopa": Luigi, Yoshi and the cavepeople turning into Chickadactyls was scary enough but the real nightmare fuel was when King Koopa wanted to turn them into KFC-like food and eat them! Neither Mario nor the princess ate the eggs, or otherwise Koopa would have won! Koopa's line really seals the deal: "One more day and it will be too late. Your friends will go from the fried egg to the fryer! And the next stop is the frying pan!" If this was meant tokeep kids away from fast food,they did a good job of it!
The monstrous Piranha Plant in "A Little Learning". First, it grows at an alarming rate when Oogtar feeds it fertilizer. Then, it leaps out a window and chases Koopa, snapping its jaws threateningly at him. Koopa, Hip and Hop hide behind a tree only for the Piranha Plant to find them and swallow them whole! Yoshi eating it immediately afterward doesn't exactly help matters.
Hip's project causing the school to explode like an actual volcano.
A fear of heights as well as death by falling makes playing Mario Galaxy and Mario 64 terrifying sometimesnote since Galaxy had falling into an endless abyss/sucked into a black hole deaths and 64 had falling damage.
The German Club Nintendo comic Super Mario in Die Nacht des Grauens(ENG) Super Mario in The Night of Horror features a zombie Princess Peach◊ with creepy black eyes and a pale, cracked face.
This image of Nurse Toadstool from the German Club Nintendo magazine has horrifyingSkintone Sclerae.