When SpongeBob enters Sandy's house he becomes dehydrated, showing his dried skin, enlarged eye holes, and a forced wide smile. Oh SpongeBob, you really need to remember to put on your water helmet whenever you go there...
Thunder Tikis, the only type of tiki that can harm you. The way they crackle with thunder as they prepare to explode is very anxiety-inducing, because you know you'll get hurt if you don't get away quickly enough.
Patrick's Dream; its nothing but a big black void with just Patrick, a lightbulb, the spatula, you, and a gate suspended in the middle of nowhere. It's obviously intended to be a joke, but it can be rather unsettling, especially compared to how Patrick's dreams are portrayed in the show. Should you try to explore the void, the layout just ends up looping and you might find yourself back with Patrick.
Then there's the cut Patrick's Dream,a dessert-themed world. While the level itself isn't scary or disturbing at all, there are a lot of things that are due to the level being unfinished. These include the skybox warping the visuals of the level into a disorientating mush of colors, random objects floating in the sky for no reason, the fact that nothing in the level works except for a few moving objects. Then there's this music, which, while not the most disturbing, is the only noise in the level. Talk about Nothing Is Scarier.
Two words: Rock Bottom. A Bleak Level if there ever was one.
It doesn't help that it introduces the Sleepy Timebots who will angrily and loudly react to being woken up by blasting you with a homing laser. They are also VERY HARD TO KILL! Having to sneak up these guys in the darkness of Rock Bottom with this playing in the background can be a nerve-wracking experience.
Granted, this becomes much easier when you get the Cruise Bubble since Sleepy Time can't detect them, but you would still have to grab at most, 15 more Golden Spatulas and fight Robo-Patrick (who has his own fair share of nightmare fuel) before you could get that ability.
The Kelp Caves. The music is a sluggish, lower version of the regular Kelp Forest music, with added background noises like the noises of cave-dwelling animals. Its combination of eerie setting, disturbing music, and cramped space is disturbing. Not helping is the fact that some get stuck in the cave for literally years before figuring out the solution...the Sleepytime robots are also scary, mainly because of the fact that it makes a loud noise when striking. For some reason, some also find the Monsoon robots scary. Not helping is the fact that one of each can be found in the Kelp Caves...
Squidward's Dream is full of portraits of his "does this look unsure to you?" face, with a huge one right behind where you start the level.
The Flying Dutchman's Graveyard. There's the haunting music. Then you meet the actual Flying Dutchman, who steals souls and forces you to fight him. However, for others, it may instead add more to fuel their awesome music side for the heck of it (as mentioned above in the awesome music entry). Additionally, the entire area is made up of hundreds of thousands of sunken and wrecked ships. Considering how all those ships were once proud sea vessels full of sailors. All those people now long dead and thier magnificent ships just rotting away in a toxic, haunted wasteland at the bottom of the sea. One of the most morbid episodes of a Spongebob game.
Robo-Patrick has several of these:
Squidward and SpongeBob getting frozen solid by Robo-Patrick's ice breath. Their extremely distorted, terrified, Off-Model expressions in the ice are really unsettling.
Robo-Patrick himself is quite different from Spongebob and Sandy's metal doppelgängers. While theirs are the usual "robotic copy with nuts and bolts jutting out everywhere" type that may slightly dip into uncanny valley for younger players, what makes Robo-Patrick different is how unnaturally alive he feels. He's the most expressive out of every robot in the game and seems to enjoy being evil, unlike the others that are only programmed to do bad. His death is also freaky: after being relatively mute during the boss battle, he lets out a scream of rage (even provided by Patrick's voice actor, Bill Fagerbakke) and explodes into pieces.
Also regarding Robo-Patrick, its health bar portrait as well, depicting it with a blood curdling scowl (which has a cameo in random TV channels triggered from hitting the TV in Shady Shoals). Said portrait is actually a ripoff of one of Patrick's artworks (him with a Valentine's Day shirt on).
His theme music also gives very awkward and metaphorical chills.
SpongeBot SteelPants's robotic voice. Especially when he laughs at you when you get hurt. Via its overall look, it even gives a new meaning of creepy with its face, considering how stiff it is compared to the original, as well as it's theme being quite dramatic for a battle. Then comes its unused phase if one gets it to work... let's just say, be prepared for a ton of freaky animations from this guy.
The 2020 remake of Battle For Bikini Bottom takes the robot designs and pushes the scare factor up to eleven.
Robo-Sandy now has a very mechanical look to her, looking purposely low poly and having a glowing red mouth. She looks absolutely frightening.
SpongeBot SteelPants especially gets this treatment. He's covered in bolts and instead of somewhat normal looking eyes, now has rather disturbing dark blue eyes. He also has very visible teeth which makes him look almost uncanny.
After nearly two decades of being only concept art, Robo-Squidward finally appears in the multiplayer campaign and he is disturbing. He has a glowing red mouth and eyes and looks incredibly menacing, especially with his tentacles flailing all over the place.
which, while not the most disturbing, is the only noise in the level. Talk about Nothing Is Scarier.