Monty Mole (1)

First off, you'll need to use Luigi's Thunderhand. Power up the orb in the area with it, and a platform will pop out of the ground nearby. Hop onto that platform using High Jump, and then head into the cave.

Once inside, you'll see a sign that tells you about these things called Simu-Blocks. The goal is to hit both of them, but they're on separate ledges, making it a bit of a puzzle. Here's the trick: have only Mario jump up the ledges to reach the top one. Meanwhile, get Luigi to move over to the right side of the area. Once you've got both brothers positioned underneath a block, you'll need to press A + B at the exact same time. Nail it, and both blocks will activate, causing a bridge to appear in front of you.

Now, you'll move into the second area. Here, you've got another two Simu-Blocks to deal with. This time, have Mario jump up the ledges starting from the right side of the area. Luigi should follow along below him. Again, you need to hit both blocks simultaneously. Success here will create another bridge ahead.

Cross that bridge, and you'll reach the final puzzle area. For this last bit, have both Mario and Luigi jump up the ledges on the right side of the pit. Get Mario to jump across the pit. This will cause Luigi to fall down to the lower area. From this lower spot, hit both blocks together. This will finally make the last bridge appear.

Cross the final bridge and find Monty Mole. Chat with him, and he'll give you the Wool Trousers as your reward!