As noted elsewhere on this wiki, the Night of the Living Dummy books is about ten times scarier when you consider the situation. They're about dummies (Slappy or Mr. Wood, depending on which book you're reading) attempting to enslave pre-teen girls. When the girls resist him, he slaps and hits them. To top it all off, in one book he demands a bride, a preteen girl, who he gives violent attacks and calls then "love taps".
Also in one of the Goosebumps books; Revenge of the Living Dummy, it is revealed that Slappy hasn't been awake for most of the book so when you think about the time Brittney was pushed the stairs by the dummy, that means that Ethan actually pushed his cousin down the stairs, just for an elaborate joke.
During Egg Monsters From Mars, the main character, Dana, is locked into a fridge cell and the titular egg monsters wrap all around him, supposedly to protect him from the cold. In the end, the protagonist (a 12-year-old boy) lays an egg while walking on the lawn. This means that the monsters did not really want to protect him from the cold, they wanted to impregnate him.
From the same book, the fate of Doctor Gray. He held the egg monsters captive in the lab and threatened their friend Dana, so the creatures strike back by burying him in a sort of "egg blanket", assumably smothering him. When Dana returns to the lab,though, there's no trace of him, and what happened is left to our imaginations. If these aliens "reward" their friends by impregnating them, what would they do to people they hate, like Gray?
Near the end of Deep Trouble, the villains try to dispose of Billy and his family by locking them in a glass tank and pushing it into the sea. A school of Merpeople show up, and Billy at first thinks they want revenge for kidnapping their friend. Fortunately, the creatures save the heroes after realizing their good intentions. Alexander and the thugs, however, don't have these ideals, and the Mermaids stop them by capsizing their boat. They're never seen again. Dr.Deep should be really grateful he stopped hunting mermaids...
Also in The Curse of Camp Cold Lake, at first you think the girl on the cover is supposed to be Della, the ghost girl that torments poor Sarah Maas all story long. Until you read and find Della looks perfectly normal but is transparent (plus, she died when she ran into the woods and got bitten by snakes. No one has ever died in the lakes of Camp Cold Lake because the counselors impose a buttload of water safety rules. This girl is not transparent and looks like a female version of the Skin Taker fromCandle Cove. The ending implies that Sarah is killed by Brinna in the Mandatory Twist Ending, though Sarah was also killed by a snake, because the story ended with Brinna holding a poisonous snake and asking Sarah to be her buddy.
According to the Horror Land spinoff books, the Goosebumps books are set in the same universe. Now just imagine the kid protagonists years later, with their own kids. What's life going to be like for them?
Chicken Chicken is horrible enough,but it gets worse when the story implies that Crystal and Cole weren't Vanessa's first victims.
In Phantom of the Auditorium, the protagonists are snooping around the titular Phantom's lair. They come across a bowl of freshly poured corn flakes, which they then assume to be a sign that the villain is near. This may sound like stupid logic, but it's actually a clever bit of deductive thinking. If someone pours a bowl of cereal and goes a short distance before someone finds it,the cereal would still be fresh. However, if someone were to go a long distance after pouring that cereal, it'd be soggy due to being left for all that time.
A Shocker On Shock Street became increasingly bizarre and insane the further it went on, up to the Erin and Marty robots short circuiting and needing to be shut down. Someone on the "Blogger Beware" website commented on the review that the insanity of the book's events made more sense when one realizes the story is being told from the point of view from a robot that has been steadily malfunctioning, so naturally Erin's perception of the world had become warped and unstable (which started when she asked her dad if her mom was coming on the ride too, and her dad sheepishly dodges the question. During the end, Erin's "dad" said that he knew something was wrong with the Erin robot when she asked about her mom, when she should have known she was built, not biologically created).
In Chicken Chicken, Vanessa turns the protagonists into chickens...because they chickened out of giving her an apology for knocking over her groceries.