These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Billy Deep from the "Deep Trouble" series always seems to get his cocky attitude and thirst for adventure back, even after surviving dangerous incidents with sea monsters, sharks, and criminals.
Most of the protagonists in the Horrorland books go through truly disturbing and traumatic ordeals, but quickly think nothing of it once they get invited to Horrorland. Justified for some, who specifically go to have fun after everything they've been through.
Canon Sue: In the TV version of You Can't Scare Me, Courtney comes off as this.
The villainous dummy Slappy. Whenever a person finds him and reads a piece of paper that has the spell to bring him to life, Slappy always tries to turn the person's family against them by framing them. But that's not all. He would try to make the family his slaves, which normally involves preteen girls. In one book in particular, the protagonist in the book throws a birthday party in the basement, and Slappy sprung to life and grabbed the birthday boy by the neck. He then threatened to kill everyone in the basement if he didn't receive a bride. The doll, Mary Ellen, offers herself as his wife, but he turns her down and was referring that the protagonist, who is a preteen girl be his bride. When she refused, he punches her, and states that it was only a love tap. death. When Slappy felt that Georgia was picking up on him, he pondered on whether or not to kill her and her family in order to avoid being caught. Slappy then ups this in the Goosebumps Horrorland book entitled Slappy New Year in which he tried to cut a boy's head off with garden shears.
There's also the Big Bad of Goosebumps Horrorland, the Menace. When he was completely alive, kids died on his rides but he didn't care, due to his experiments in fear. The park was so scary, it somehow ended up in an alternate universe. Later, he found out Horrorland was made on his park, so he got contact with a horror to invite guests there so he get them to panic park, and make them bring the fear meter up so he can PP back to the normal world. it's implied he's done this before...but the previous kids got so scared they died and he simply doesn't care. He even got several other goosebumps villains to follow him, including Slappy, and King Tutten-Ra from another GBH book. However, this could also be a case of Blue and Orange Morality, since the Horrors had their own set of morals.
Mr. Toggle from Piano Lessons Can Be Murder is a self-described brilliant robotician who runs a piano school that Jerry is sent to by his parents. Initially appearing to be a harmless, if eccentric figure, Toggle soon reveals himself as a particularly depraved Mad Scientist. Despite his status as a famed robotician, he couldn't make robotic hands properly. So, he lures men, women, and children alike to his piano school and cuts their hands off and uses them for his experiments in hopes of creating beautiful music, all to satisfy his ego. (The TV Adaptation even implies his first victim was his mother.)
Karl, from the Goosebumps TV Series season 3's three-parter "Chillogy," gets sick pleasure out of physically and mentally torturing kids simply because it's his hobby. He transports them into his miniature town and personal playground Karlsville, where he toys with them before he plans to kill them. He manipulates Jessica into pursuing her own greed to sell more of his lemonade, then turns her into a pig and sends a mob of angry townspeople after her to serve her up to him for lunch. He plays a lethal game of baseball with Matthew where Matthew has to do such things as fight a team of monsters, dodge killer baseballs, and crawl over a lava pit to make it to the next base. His last victim is Matthew's brother Todd, whom he prepares to "make a citizen of Karlsville" by turning him into a small plastic figure who will be forever conscious. He delays Todd's fate as long as he possibly can to enjoy Todd's fear.
Slappy, who wasn't even the main villain in his first story, ended up becoming the series' mascot.
And Andy, the female friend of Evan Ross, the protagonist of the "Monster Blood" series. Many fans of the series, especially readers of Blogger Beware, wish that Andy would have been the protagonist instead of Evan.
Della Raver may also be considered one, if only because she was much more likable and interesting compared to the actual protagonist of the book she was a villain in. If anything, the fact that she was able to gain a section in the Characters page before Sarah Maas just shows how much the readers actually prefer Della.
First Installment Wins: Many people consider the original 62-book series to be the best compared to its numerous spinoffs.
A lot of the stories centered on kids being made fun of and wanting revenge, fearing for their lives at school (or children dying or said to be dead) are more depressing to read in this post-Columbine/Virginia Tech/Newtown world.
In the TV adaptation of "Say Cheese and Die!", Doug said "News flash! This is a camera, not a weapon!"
Jerkass Woobie: Della, the titular ghost of The Curse of Camp Cold Lake. She's not really evil, it's just that she really wants to escape from her existence on the lonely camp grounds.
Magnificent Bastard: In "Attack Of The Mutant" the titular villain spends the entire book in the form of a twelve year old girl, takes advantage of his own comic story to lure Skipper to his base, has everyone fooled(including his henchman, who he kills in his little girl form), and never makes his presence known until the last few chapters. He'd probably be a more effective example if he wasn't so gullible and petty.
A strong occurrence in the TV adaptation mostly due to the mediocre child actors.
Also frequent in the books themselves. Sometimes it's hard to believe Stine has ever heard children speak before.
Replacement Scrappy: Dr. Maniac to The Masked Mutant. While the Mutant was apparently popular enough to get his own video game, her never reappeared. Dr. Maniac, who's story is an obvious Spiritual Successor, not only got a sequel, but a recurring role throughout the Horror Land books. The only villain to show up as much as him is Slappy.
A young Ryan Gosling, well before he became a movie star, appeared as Greg Banks inSay Cheese and Die.
Scott Speedman, also young and up and coming at that time, did a cameo in Say Cheese and Die as a policeman.
Also Hayden Christensen as the nerdy cousin in Night of the Living Dummy Part III.
Laura Vandervoort is one of the protagonists in The Haunted House Game.
Rooting for the Empire: If the book's protagonist is too whiny, annoying, or just keeps doing stupid things, chances are the reader will start hoping the book's villain will do something really horrible to them. Case in point, The Curse of Camp Cold Lake and some of the Monster Blood books due to how unlikably whiny Sarah Maas and Evan Ross are.
Tastes Like Diabetes: A Holly Jolly Holiday, about a disgustingly sweet Christmas movie available on a cursed video cassette that brainwashes a family into acting as cheery as its main character, Susie Snowflake (until the main character turns on a wrestling match while rewinding the tape and the family snaps out of it).
When Horrorland was launched it included reprints of classic Goosebumps stories as companions, although some of the accompanying reprints don't really match up with the Horrorland books. The original Horrorland story was reprinted alongside Dr. Maniac Vs. Robby Schwartz, even though Attack of the Mutant seemed like a more natural choice. Weirdo Halloween received The Scarecrow Walks At Midnight instead of Attack of the Jack-O'-Lanterns which was also a book about kids dealing with aliens on Halloween.
The Horrorland series in general has this problem. While intended to follow up on many of the original books, many of them only vaguely resemble older books, and many of them only feature the same supernatural elements rather than returning protagonists. As a result, the group in Horrorland is made up mostly of new arrivals. Some fan favorites, such as Attack of the Mutant, did not receive any follow up at all.
They Wasted a Perfectly Good Character: The Masked Mutant actually manages to be a competent, threatening and mysterious antagonist. He's killed off in his only appearance-and in one of the most ridiculous ways possible.
Wangst: There's quite a bit, considering it's an adult writing through the viewpoint of twelve year olds, but Sarah from Curse of Camp Cold Lake really stands out.
Some of the kids go to Horrorland specifically to relax and distance themselves from their horrific adventures... they go to Horrorland to do this.
Abby from Who's Your Mummy in particular is shocked and horrified when she encounters a mummy themed attraction, wondering if someone specifically put it there to frighten her. In a Horror themed amusement park, a single mummy based attraction can't be that surprising, can it?
Carly Beth Caldwell, especially in the TV show, and especially Crystal and Cole.
Gary Lutz in Why I'm Afraid of Bees. He's picked on by bullies, his sister hates him, her cat hates him, his attempt to impress a girl ended with him crashing his back, and when he has a chance to get a better live, he turns into the very thing he hates most. Let's just say the point where he wants to sting someone, and thus die after isn't entirely out of nowhere.
Michael Webster in The Cuckoo Clock of Doom. He's The Unfavorite to his complete brat of a younger sister, his parents make fun of him and call him a liar when he tries to tell them how she makes his life miserable, and it's all but outright said that his dad thinks he's stupid. It says something about your life when having your sister erased from existence is a good thing for you.