From the Super Mario Wiki
Fret is a resident from Flipside's second floor in Super Paper Mario. His hobby is writing all the things he wants to do before his game ends, but he has not accomplished any of them. He appears to play minigames at the Flipside Arcade, since he holds multiple high scores: 200,000 in Tilt Island, 300,000 in Hammer Whacker, and 400,000 in Mansion Patrol. He is very fond of the four heroes for saving all worlds. He has a Flopside counterpart named Chet.