PokeGen is now maintained by Mat.
Current version: 3.1.13 <-- THIS IS A LINK, SINCE PEOPLE DON'T GET IT
Be sure to always keep backups of your save files prior to editing. I'm not perfect, mistakes can exist in the program still.
This program can be used for Diamond, Pearl, Platinum, Heart Gold, Soul Silver, Black, White, Black 2, and White 2 for the following tasks:
Generating Action Replay codes to create Pokemon, modify the Pokedex, and add Mystery Gift data, inc