The Boots of Ostara have a 50% to drop from Lepus. It is equipped in the armor slot, with just 3 defense given. Once equipped, the Boots of Ostara fertilizes the soil and allows the wearer to perform a bunny hop. If the user keeps jumping, they will jump higher every time until they reach a maximum height. This is useful when fighting flying monsters, such as Harpies.
In the St. Patrick's day Terraria icon, the person seems to be wearing this.