A colored background means that the Pokémon can be found in this location in the specified game. A white background with a colored letter means that the Pokémon cannot be found here.
Mt. Moon was once comprised of a large cave network, but recent collapses have left only a single chamber connecting Route 3 to Route 4. Silver appears not far from the entrance and challenges you once again. After he leaves, climb the ladder to the east.
At 8:00 PM on Monday nights, two Clefairy appear in the field and start dancing around a large rock. When you enter the field, they get startled and run away, leaving the rock behind. If you break it with Rock Smash, a Moon Stone can be found hidden underneath. The two Clefairy return to worship the moon every week.
Enter the south side of the cave for a shortcut to the exit.