Arriving in Monstro Town in Super Mario RPG if you take a nap in the bed you'll be greeted by the Three Musty Fears. They'll challenge you to locate three invisible flags hidden around the world and as a reward, you'll obtain one of the best badges in the game.
How to start the Three Musty Fears side quest
Entering Monstro Town enter the house with the single bed in the middle and the glowing mushroom in the corner. Interact with the mushroom to turn off the light and go to bed.
During the night you'll be informed by Greaper, Dry Bones, and Boo as to the challenge you're being given and where they've hidden their invisible flags.
Their hints are:
- Behind a wooden flower
- Under a green bed
- It's between O and A
Three Musty Fear Flag Locations
You can find each of the invisible flags in the following locations:
- Behind the wooden rose sign that's at the entrance to Rose Town
- Underneath Mario's bed from the beginning of the game
- Between the O and the A in the word Goal on Yo'ster Isle
After you've obtained all three flags you can return to Monstro Town and sleep in the bed again. When the Three Musty Fears see you've collected all of the flags you'll get the Ghost Medal which when equipped doubles your defence during battle.