In paper Mario how do you get past the skull rock at keyhaul key?

In Paper Mario, to get past the Skull Rock at Keyhole Key, you need to use the Boomerang ability of your partner, Bombette. First, you need to find and defeat the enemies around the rock to clear the area. Then, you can have Bombette blow up the rock, creating a path forward. Once the rock is destroyed, you can continue on your journey.