Pikifen (formerly known as the Pikmin fangame engine) is a real program made by Espyo that is capable of creating and playing Pikmin fan content. It is an open-source engine, currently under development, that can handle gameplay similar to the Pikmin games, in that it allows leaders to whistle and throw Pikmin, allows Pikmin to carry objects, etc. Although the idea is for fans to create their own content (enemies, areas, etc.) so the engine can read it and turn it into something playable, the current download also comes with some pre-packaged content, which makes it possible for people who download it to experiment its features right away.
The reason for its creation was to make it possible for fans to make their own Pikmin fan content and to be able to play on it, by requiring only assets and data, while the engine itself handles all of the more complicated parts like the physics and artificial intelligence. It is currently under development, and alpha versions are available for download. The engine can run on Windows, Linux, and Mac.
DISCLAIMER: Pikifen and any fan content run within it are not affiliated with Nintendo® and should not be sold. They are non-profit projects created by fans of the Pikmin® franchise, and do not intend to infringe on the copyrights or registered trademarks of Nintendo®. Pikmin® is a trademark of Nintendo®. The copyrights of all associated characters, names, terms, art, music, and assets belong to Nintendo®.