How do you unlock baby luigi in mariokart wii i cant get any expert ghost staffs what the heck should i do?

Go to cheatcc.com to check the time for each stage that has to reached to unlock fast staff ghosts. If you unlock enough fast staff ghosts, you will unlock certain characters and vehicles. If you unlock all fast staff ghosts you will unlock Mii outfit B(when this answer was being typed, the only fast staff ghost time that I can remember is of Rainbow Road's, which about 2:59).