Instructions
Attend a Nintendo Event. Bring "FireRed" or "LeafGreen" with you. During this event, approach the "Wonder Spot" machine and connect using the "Mystery Gift" feature of the game. This will grant you the "Mystic Ticket," which must be used to encounter Lugia and Ho-Oh. Nintendo events can be found on the official Pokemon web site (see References).
Insert "Emerald," "FireRed" or "LeafGreen" into the bottom slot of the Nintendo DS system. Turn on the system. Players can expect to encounter a shiny Pokemon once in every 8,192 battles.
Go to the Vermilion City port. When prompted by the sailor, select "Navel Rock." It is in the Hoenn region, north of Slateport City. Enter the only cave on the island, proceeding until you encounter a staircase. The player can go either left or right.
Save your game. Go right and down a series of steps until you encounter Lugia, which appears at Level 70. Enter into battle with Lugia and take note of its color. A shiny Lugia may appear to have bold red colors along its eyes and other body parts, along with its usual white color. If Lugia appears to be a typical Lugia, reset your game. Repeat this step until Lugia appears to be shiny.
Enter into battle when you encounter Shiny Lugia. Weaken it and use an Ultraball to capture it. In the "Summary" screen of your game, a red star will appear beside Lugia's image, indicating that it is shiny. Save your game.
Return to the hallway where you encountered the first staircase. Previously, you went to the right. Go to the left and travel up a staircase. You will encounter Ho-Oh at Level 70. If Ho-Oh's color appears normal, reset your game. Repeat this step until Ho-Oh's colors change.
Weaken Ho-Oh in battle and use an Ultraball to capture it. You also determine with certainty that it is a shiny Pokemon in the "Summary" screen. If a red star does not appear in the "Summary" screen, it is not a shiny Pokemon.
Save your game and turn off the system. Insert "Diamond" in the DS game slot on the Nintendo DS. Turn on the system. Select "Migrate from..." in the main menu. Select Ho-Oh and Lugia to permanently transfer from "Emerald," "FireRed" or "LeafGreen."
Travel to the Pal Park in "Diamond," located along Route 221. Enter the Pal Park. You will catch the Pokemon you transferred 100 percent of the time using the park's Pokeballs. Wander until you spot Ho-Oh and Lugia in random encounters. Throw Pokeballs to capture them. Save your game. You now have shiny Ho-Oh and shiny Lugia in your copy of "Diamond."