Most of the time, Scareactors will jump at you and go "boo!" I try to avoid them by walking on the sidewalk or following a group of people really close. The haunted mazes are about the same. Things go boo and bump in dimly-lit corridors.
There is a Festival of the Dead parade, which is basically a Mardi Gras parade with a Halloween theme. The major rides are usually open. Since it is at IOA this year, I would expect the big rides like the Hulk and Spider-Man to be open. Triceratops Encounter may close for the night (sorry).