Go to a man near Five Island. If he tells you, the first Pokemon in your party is happy, he'll give you an egg. It will hatch into a Togepi. Use some Carbos, Protein, Rare Candies etc. on it. Give it an Exp. Share to hold. That way it will gain levels without battling. At a level in the 30's, it will evolve into Togetic. You can also trade Togetic from Colloseum.