Grover wore his fake feet and his pants to pass as human. He wore a green rasta-style cap, because when it rained his curly hair flattened and you could just see the tips of his horns. His bright orange backpack was full of scrap metal and apples to snack on. In his pocket was a set of reed pipes his daddy goat had carved for him, even though he only knew two songs: Mozart's Piano Concerto no. 12 and Hilary Duff's "So Yesterday," both of which sounded pretty bad on reed pipes.
Rick Riordan (2006). “The lightning thief”