Successfully complete the indicated task to unlock the corresponding costume:

Baseball: Sink a Rising Ball shot. 
Biker: Sink a Double Eagle shot. 
Kimono: Sink a Flag Ball shot. 
Pickaxe: Sink a putt from over 40 feet away. 
Police: Sink a homing ball. 
Poncho: Sink a spiral shot. 
White Tuxedo: Chip a shot in for birdie or better. 
Witch: Get a hole in one.