Originally Posted by scorchio1158
How do you get Mirage Island to appear?
This is answered in the Read First guide:
2. How do I get to Mirage Island? What's there?
Mirage Island appears at random. Every day, a number between 1 and 65536 is chosen, and if this number matches one of your Pokemon, then Mirage Island will appear on Route 130. The previous theory about gender modifiers was proven false.
So, if you really want to go there, visit the old man in Pacifidlog and bring all of your Pokemon to him EVERY DAY. If you're lucky, he'll say he can see the island.
Mirage Island is filled with Wynauts, and it's the only place where you'll find the rare Liechi Berry.