From the Super Mario Wiki

Bean, the cowboy from the GBC game Mobile Golf.

Bean (ビーン Bean) is a rowdy, childish golfer in Mobile Golf for the Gameboy Color. He is the champion of the first tournament that you must defeat in singles. Along with Rozary, Powert and Bird, he is one of the four human golfers you must face in four singles tournaments, similar to the fashion of Mario Golf (GBC).

According to his profile on Camelot's Japanese Mobile Golf website, Bean is a mischevous little boy who was raised on the ranch. There he not only does his daily deeds as a cowboy, but he practices golf as well. It is unclear whether or not he is younger than Kid, who became a legendary golfer at the age of 10. His Mario Golf counterpart would be Putts.

[edit] Trivia

• His name "Bean" is a pun on bean, possibly implying his size and stature as a young boy.