Getting jumpscared and bitten by evil animatronics? Not funny, unless you're watching someone react. Getting jumpscared by a homicidal cupcake with razor-sharp teeth? Hysterical!
The fact that you can play as the Crying Child (who, mind you, is a dead kid's ghost) along with all the more light-hearted and colorful cast of characters.
In a meta example, fans are not above making a team of the Crying Child, Nightmare Fredbear, Nightmare, and another random Nightmare animatronic of their choice for kicks.
The teaser for Update 2 informs that we can actually play as the Purple Guy AND Scott Cawthon. Let that sink in for a moment.
The ending with two Fredbears glitching out and exploding because of a time paradox, which wipes out the universe shortly after is mildly disturbing and funny, and your "reward" for doing this is a shiny, silvery trophy of Fredbear's lower half.
Some of the lawsuits you can get are downright ridiculous, such as a child who supposedly went into a coma and woke up "essentially lobotomized" all because... she saw an animatronic's head fall off. Even the justified claims can be darkly humorous because of how stupidly dangerous you've made your children's restaurant.
The Toy Chica cutscenes, which are gradually more and more obvious about her mental state; by the time she gets to Mangle, she says that she'll tell him she's taken several live hostages.
Roxanne being damaged and her state afterwards (both physical and mental) is certainly terrifying yet depressing, if not for the Repeat Cut that shows Roxanne's beautiful Oh, Crap! moment, as well as the kart hitting her straight in the face. It's hard not to laugh when seeing this.
to Dawko's demand that 50/20 mode be easier? Accidentally let slip that 51/20 mode will, in fact, be easier. And this came after Dawko made his demand