- Jossed. It was Stine's very first manuscript.
- Slappy's ability to bring monsters to life. We've seen that if he gets a way of expanding his power, he can create monsters out of anything. The next movie has potential to upgrade this to Becoming the Costume with humans.
- Slappy wants a family. Of humans, of monsters, it doesn't matter; he just wants one. This is actually a slight carryover from the first film in that he considered all of Stine's other creations his friends and companions, and his overall goal was to make sure none of them had to go back to their books. It's even slightly hinted to in the first movie, with his use of "Papa" to refer to Stine, and how in this one, a Broken Pedestal lead him to flat-out disown him in this one. This in and of itself is Slappy's goal/character arc.
- Slappy learns from his mistakes. He started this movie out by acting like a decent person to get Sam and Sonny on his side, whereas in the first film, he was an outright bastard from the get-go. He also made damn sure to get the Haunted Halloween book in his possession ASAP, and showed shades of manipulation to both humans and monsters. And now he's written a book to take out Stine, because he knows Stine is the biggest threat to him.
- R.L. Stine is no longer a threat. As mentioned, Slappy took him out by imprisoning him in a book of his own. He can also go wherever he damn well pleases, which means he's most likely going to get the book from the first film next and bring his friends back, get Haunted Halloween, and destroy them both. With Stine out of the way, and no one who knows these characters as intimately as he does, Slappy and his monster friends can bring Horrorland into our world.
- With a family comes a home for them. Where is Slappy's family going to make their home? Horrorland.
- We have two movies now where trapping characters in a book is the only way to get rid of them, and both times, someone didn't get pulled in (the Invisible Boy and Slappy, respectively). There's one core difference here: the Invisible Boy was a one-off joke/twist that didn't come back. Slappy, however, has staying power because "I always survive; you wrote me that way," and thus there will be consequences this time around. Combined with his savviness that increases in each film, the next one may find a different way to get rid of the monsters once and for all.
- Horrorland as a book series had a set-up where all the characters from the previous books joined together in the final book of their given arc. There's some Fridge Brilliance in having a new set of characters not only due to the original series being anthology, but because of the Horrorland spin-off, it could mean Zac, Hannah, Champ, Sam, Sonny, and Sarah all end up at the Horrorland park and use their combined knowledge of their experiences to take down Slappy and his gang once and for all.
- Since the movies have their own mythology from the books, it's possible the writers wanted to save Horrorland for the Grand Finale of a trilogy.
Playing a little off the above theory, Jimmy O'James, a ventriloquist who worked with Slappy, will be Slappy's (unwilling) dragon, seeing as it would be beneficial to have a human as the face of the park while he pulls the strings behind stage. If not Jimmy himself, then at least a similar Unwitting Pawn.
Nothing would be more meta than for Mr. Wood to be the final twist in these movies. The characters FINALLY get rid of Slappy, only to find a similar, redheaded dummy is lurking around and making a comment along the lines of, "Now I can get MY story back." Since Mr. Wood was the villain of the first book with Slappy coming to life being the twist, it would be a nice little homage/reversal.
While it can simply be chalked up to a neighbour who can't take living next to a creepy abandoned house anymore, it seemed weird that despite clearly charging for their services, payment is offered under the supposedly monetary value of the items themselves rather then an actual payment. Under these circumstances, anyone who realised this fact will try to loot the abandoned house for actual artefacts to sell.
In the process of doing so, they will inevitably uncover and open the Haunted Halloween book, effectively starting everything up to possibly leading to the events of Horrorland or even something bigger.