Luigi
From Paper Wiki
Luigi is Mario's younger brother in the Mario series.
Paper Mario
In this game, Mario and Luigi are invited to Peach's party at her castle. Before Bowser had taken over her castle Luigi managably escapes. For the rest of the game, he is at home begging Mario to go on the adventure with him. If Mario gains the Super Boots and sees a loose panel at his house, it is revealed that Luigi has a diary.
