Instructions
Start up "Pokemon FireRed" or "LeafGreen" on the first Nintendo Game Boy Advance.
Find a Caterpie either in the Viridian Forest on Route 2 in the west of Kanto, or on Route 25 in the northeast.
Use a Flying, Rock or Fire-type Pokemon to wear down Caterpie's health points and catch it in a Pokeball. Go to the nearest Pokemon Center and go upstairs to the Cable Club.
Start up "Pokemon Emerald" on the second Game Boy Advance and go to the Cable Club in the nearest Pokemon Center.
Connect the two Game Boys using the link cable.
Select Caterpie in the "FireRed" or "LeafGreen" game and trade it across to "Pokemon Emerald."