The Zoo Tycoon series had six expansions.
Board games and RPGs have been marketing expansions since at least the early 1970s. While board game expansions are typically designed by the original creator, video game developers sometimes contract out development of the expansion pack to third-party company, or it may choose to develop the expansion itself. These add-ons usually add new game areas, weapons, objects, and/or an extended storyline to a complete and already released game. An expansion pack is an addition to an existing role-playing game, board game or video game.
