Secret Scroll 1
From the Super Mario Wiki
Secret Scroll 1 is a key item in Mario & Luigi: Superstar Saga. After obtaining the Super Hammer from the Hammerhead Bros., Mario and Luigi can go to the first room to the right of Sledge and Mallet's new home. There is a Thwomp named Thwomp there. One of the prizes for winning the minigame is this scroll. After reading the scroll, Mario and Luigi learn the Swing Bros. move.