Another neat fact: Jirachi is probably the least-available Mythical Pokémon with the least thought put into it.
Mew - Faraway Island, transfer from My Pokémon Ranch
Celebi - Ilex Forest (Crystal), Japanese Colosseum bonus disc
Lugia - Whirl Islands, Navel Rock, transfer from XD, transfer from Dream Radar, Sea Mauville (AS)
Ho-Oh - Bell Tower, Navel Rock, transfer from Colosseum, transfer from Dream Radar, Sea Mauville (OR)
Jirachi - American Colosseum bonus disc
Deoxys - Birth Island, transfer from Guardian Signs, Delta Episode
Phione - breed Manaphy, My Pokémon Ranch
Manaphy - transfer Manaphy Egg from Ranger/Shadows of Almia/Guardian Signs
Darkrai - Newmoon Island, transfer from Shadows of Almia
Shaymin - Flower Paradise, transfer from Guardian Signs
Arceus - Hall of Origin
Victini - Liberty Garden
Keldeo - distribution, but has specific features in-game (tutor, Resolute Form, special dialogue)
Meloetta - distribution, but has specific features in-game (tutor, special dialogue)
Genesect - distribution, but has specific features in-game (Drives, special dialogue)
Diancie - distribution, but has specific features in-game (Mega Diancie, special dialogue)
Hoopa - distribution, but has specific features in-game (Hoopa Unbound, special dialogue)
Volcanion - distribution, but has specific features in-game (special dialogue)
Magearna - QR code distribution, special dialogue, Original Color form
Marshadow - undistributed so far, but has Marshadium Z
There has never been any special dialogue, forms, or tutor moves for owning a Jirachi at any point in time, and the only way to obtain it outside a plain old distribution is a single region's bonus disc (not even Japan's) for Colosseum.
