Here's what a guy posted, have a good laugh at it xD (yes there are answers to some other things that have nothing to do with Jirachi)
How to get Jirachi: Go to Mossdeep city, where you can find that white stone and bring an Altaria and an Absol, both Lv. 100, press A on the rock and Altaria will sing, making Jirachi appear.
How to get Jirachi: Defeat the Pokemon league 100 times, then go to Professor Birch and he'll give you the desire sticky that you must use on the white stone in Mossdeep city.
How to get Jirachi: After the mirage island appeared, don't take the berry, go to the pokemon league and let Rocco win, then return to the mirage island and you'll find Jirachi that is eating the berry and you can catch it.
How to get Jirachi: After defeating that mage in those quiz, go and look for him in the victory road and if you find him, he'll give you a free Jirachi. How to get Jirachi: After getting 100 missiles launched from the spacial center, talk with the girl near the white rock, press A on it and Jirachi will appear.
How to get Deoxys: After defeating the pokemon league 100 times, if you search underwater you'll see that there is a hole where you'll find Deoxys.
How to get Deoxys: When you get the red sphere or the blue sphere, let a friend send you the other sphere. When you'll go in whatever route, those spheres will explode, making Deoxys appear.
How to get Deoxys: After getting 250 missiles launched from the spacial center, go to your mom and she'll give you a ticket to go with the rocket, where you'll get Deoxys.
Rejis: If you catch the three Regis, the door in the house in Mossdeep city will unlock and you'll find an item. If you give it to one of the Regis and trade it, the three Regis will fuse themselves in a SUPER-Pokemon much powerful, with a typing of steel, ice and rock.
How to get Feebas: To get Feebas, you must listed for the cry of Milotic when you are fishing.
Go to Kanto/Johto: If you manage to defeat the pokemon league with only one Lv.50 pokemon, when you return to Ever Grande City with surf, you'll find another cave near the victory road called "??? cave". If you go past it, you'll find out that you are now in Kanto and you can go to Johto from there.
My Resident evil Code Veronica X run: http://www.gamefaqs.com/boards/445328-resident-evil-code-veronica-x/55833337 http://www.youtube.com/watch?v=y_aXS0n2KGQ