User Expansions are expansion packs for the base Zoo Tycoon 2 game made by fans and designers that have not been directly authorized by Blue Fang Games or Microsoft. They imitate official expansion packs by generally adding roughly 15-25 animals and a variety of bonus content, including a filter and an icon on the main menu. Only one user expansion was every completed for the original Zoo Tycoon, known as Wild Wings, created by RSN in 2003.