How do you get jarachi?

Answer 1

You have to migrate it from other games, trade it in GTS or coming sometime soon there will be a mystery event on jarachi which you will obtain him at level 5 and he will know 4 moves he will have a classic ribbon and be holding sometype of berry.

Answer 2

For Pokémon FireRed and LeafGreen you need to arrange a trade with someone who was able to retrieve Jirachi from either a Nintendo distribution or from the Pokémon Colosseum bonus disc. The Colosseum bonus disc would allow you to download Jirachi into Pokémon Ruby and Pokémon Sapphire once per save file. For Pokémon Diamond, Pearl, Platinum, HeartGold and SoulSilver you will either need to have retrieved it during a DS distribution or you will need to have Jirachi that you downloaded from your bonus disc into your Ruby or Sapphire save file and then you will be able to upload it to Diamond, Pearl, Platinum, HeartGold or SoulSilver via the migration feature.