No there is no Mario character that starts with a J
Jasmine and Jafar are characters in Aladdin. They begin with J.
johnny bravo.
Jerry as in Tom and Jerry.
Lakitu. Known best for acting as an enemy in the Mario platformers.
Easy, Jane from the novel/movie Spiderman.
The Joker?Juggernaut (X-men)
Jerry, from Tom and Jerry
Judy Jetson the jetsons the jetsons
Jade or Jackie Chan from Jackie Chan Adventures.
You cannot switch characters while in game for Mario Kart DS or Wii. You can choose your character in the selection screen before the race starts though.
Japan is an island that starts with J.
the best character in Super Mario is cat Mario