Wear this to use Sleepy Stomp. 2 FP are required to use this attack, which can make enemies sleep if executed superbly. Wearing two or more of these badges requires more FP for the move, but enemies stay asleep for longer.
When equipped, for 2 FP, Mario can jump on his enemies and put them to sleep for a few turns. It costs 1 BP to put on. You have two options to get it. You can buy it at the Lovely Howz of Badges after Chapter 1 for 75 coins. Or, you can get by finishing 10 levels of the Pit of 100 Trials. The badge Sleep Stomp from Paper Mario is exactly the same, the only difference is the name.