Premise: Howl-O-Scream is an annual special event that occurs at Busch Gardens Tampa Bay, Busch Gardens Williamsburg, and SeaWorld San Antonio. The parks remain operational during the day and transition to Howl-O-Scream at night. The event features haunted houses, "scare zones", and live entertainment. It is a seasonal event that occurs in the Fall of the year, tied to Halloween.
Hypothesis: Howl-O-Scream has been happening for many years