On Star Hill, you can find some stars with a face on them. If you talk to them, you read someone's wish. Most of them come from characters in the game like Mallow, Croco, and Belome. There is also one with Mario's brother, Luigi! (Luigi's wish is that he could be a great plumber like his brother, Mario.)
Credit goes to: http://www.rpgclassics.com/shrines/snes/smrpg/secrets.shtml Except for the part in parentheses.