InAWorld where imaginary beings aren't just the product of a child's mind, and are actual living creatures, it wouldn't be surprising that beings that are the [[NightmareFuel stuff of nightmares]] would come into existence as well.

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* Let's face it, ''Destination Imagination'' got pretty creepy at times. Especially whenever World got mad...
** Destination Imagination was horrifying! Think about it--the goo that makes copies of you which come to life as zombies, the faceless beings that are completely unresponsive, not to mention the face that can take on whatever image it pleases!
** [[ArsonMurderAndJaywalking And This is the Only Foster's Episode/Movie to be Rated TV-PG!]]
* Also Wilt's {{backstory}}. [[spoiler: Y'know how he's missing an arm and in the first episode, he explains he used to play basketball but now can't? It is because one of his basketball opponents '''slammed him into a wall''', crushing his arm beyond repair and (although not actually shown but fairly obviously implied) causing it to be amputated.]].
** A ByTheLightsOfTheirEyes gag in "Blooooo" shows that [[spoiler: the crushed eyestalk doesn't see, so Wilt only has one working arm and one working eye]].
** [[spoiler: It's done again in Destination: Imagination. But both his eyes are seen in the gag]]
* ''Berry Scary'' is right...Berry's facial expressions coupled with her insanity...
** Terrence imagines a pizza friend...and then promptly ''eats'' him. Played for laughs.
*** Not if you realize what that poor pizza went through... "How-dee-doo! I luh-ove ''you''- '''AAAAAAAAAAAAAAAHHHHH!!!!!!!'''"
* That episode where Bloo catches a cold and turns white. I forget the title but there's an extended ShoutOut to ''Film/IKnowWhatYouDidLastSummer'' and until the end of the episode where we see that the guy is just a friend looking for the house, it is ''really'' creepy.
* The episode where Bloo accidentally gives Mr. Herriman a heart attack from his Halloween prank and he comes back as a zombie. [[spoiler: Sure it was a prank to get back at Bloo, but it was still damn creepy!]]
* The creepiest parts were probably the slow shots of a mostly empty Foster's. The place is so huge it would be really creepy to move through it at night. On top of that, the show makes some good use of NothingIsScarier when Bloo goes back to get the snake-in-a-can gag.
** And in the same episode, Wilt wears a fake arm on his amputated nub that pops off to spook kids. When you learn his backstory, it becomes a FunnyAneurysmMoment.
* We all know that Berry is a {{Yandere}} to the highest order, but then there's "Affair Weather Friends". [[spoiler: She kidnaps a family, hijacks a large house and disguises herself as a rich kid to lure Bloo away from Mac and keep him to herself. Oh and she has a StalkerShrine.]]
** [[spoiler: She also attempted to run Mac over with a toy train.]]
* Was I the only one a little creeped out by Mac going sugar crazy in the episode ''Partying is such Sweet Soiree''?
* Goo in general. She herself isn't scary, but the fact that she has no control over creating imaginary friends, to the point that her parents stop by often (they actually give a measurement of time in the show, every few weeks or something like that) to drop off bumper crops of friends she's created by accident. At one point she thinks that she's got it under control, only to wake up one morning with her room full of friends that she described earlier in the episode but thought she had surpressed. It ends up getting played for laughs in the group picture episode, where Herriman asks her to make a few friends that are similar to ones that just got adopted so that he doesn't have to rearrange everyone. She spends most of the episode refusing to do it (as she's fully aware of how much of a problem her power is), but they eventually slip out when she's a little distracted; she's pretty shocked by it, but Herriman takes it all in stride because now the picture is back on track.
* [[NightmareFace This]] [[http://www.fosters-home.com/screengrabs/1/15-0028.jpg face]].... This face that Frankie makes... *shudders*
* It's a more subtle one, but it puts what Charlie said in "Dinner is Swerved" into perspective. In "Seeing Red", before imagining the title character, Francis unwittingly imagines a pizza slice friend that's all like: "Howdy Do! I love you!". Then he EATS IT! YOU CAN EVEN HEAR IT SCREAM IN TERROR AS IT'S EATEN! This episode without a doubt PROVES that while imaginary friend may not die of old age, they're just as mortal as we are!
* In "Squeeze the Day" the rest of the people at Foster's leave Bloo alone so they can enjoy a day at ghe beach peacefully. He and Mac end up trying to make the most fun out of having the house alone. They go into an elevator and experience an ElevatorFailure but survive right before it hits the ground. If they hadn't had the rope... Not to forget the legal issues this would probably cause Foster's, especially since Mac's mom wasn't even aware of this. Many, if not, all of the friends would probably need to leave if worst case happened.
* "Mac Daddy" has a long montage where Bloo, after having been annoyed with Cheese all day is looking for him after he got lost. He starts to imagine Cheese getting hurt by random objects he finds. As he gets incrasingly worried, the imagine spots gradually come at a faster pace and start getting more and more intense. Sure, a lot of it is funny, but [[AdultFear Bloo's worry and the realization that, yes, Cheese IS very likely to get hurt on his own]] starts getting to you after a bit.
** In addition, the way in which the imagine spots are very crudely-drawn and with the out-of-tune music playing both compliment the distressing imagery to the point that it becomes disturbing.