Corkscrew Follies is the first expansion for RollerCoaster Tycoon that adds new themes, 32 new scenarios (including one "real" park - Alton Towers, and a previously downloadable one - Fort Anachronism) and new rides.
New gameplay-oriented features are added as well. Certain roller coasters are updated to support more complex designs with bigger loops, and more ride types can change their paintjobs. One of the most useful additions are banners that can be erected on footpaths, containing either text meant for organization purposes or a "No Entry" command, which prevents everyone, except the park staff, to pass through that footpath. A new setting in the options window allows for replacing all guest numbers with randomized names (e.g. Guest 780 becomes John D.).