Reading list: Goosebumps Horrorland
The third Goosebumps series.
This series is split into two arcs, with a "survival guide" releasing between the two.
It features Horrorland and many other monsters from previous Goosebumps adventures- and Slappy, of course.

Slappy New Year has the same title as one of the books from the cancelled series "Goosebumps Gold", but has been confirmed by Stine to not have the same plot, leaving the Gold version a mystery of what coukd have been to this day.