In the Valley stage, if you knock the Mankey off the hill and then onto the switch, you will get into Professor Oak's cabin. He will start telling you that he is there in order to follow up reports that Pokémon have been sighted as landmarks on the island. He requests that you go around taking photos of these Pokémon Signs. He opens up a Pokémon Sign bit in the Pokémon Report and as such you must go and take the photos in order to access the final level.
