Bowser Koopa Junior is Bowser's eighth son and is the youngest of the Koopalings after his big brother, Larry. However, he is his father's favorite child. Bowser Jr. is a perfect son to his father, as he wants to do nothing but his father's will. The evil king himself even shows emotions toward his new son, a side of Bowser that is rarely seen. Since he made his first appearance, he was working with his father years ago, causing trouble to Mario, Luigi, Yoshi and kidnaping Princess Peach. Meanwhile, his abilities have improved a lot recently, gaining some new incredible abilities and has now learnt how to spit fireballs in New Super Mario Bros. Wii. (but not at the same level as Bowser and Ludwig Von Koopa) He also uses his own powerful weapons and vehicles to fight against Mario(he now has his own personal Koopa Clown Car).

Any Bowser Jr. voice works since they both sound the same, here's a sample of their takes: https://www.youtube.com/watch?v=qPJ2GgSgiu8&pp=ygUaYm93c2VyIGpyIHZvaWNlIGNvbXBhcmlzb24%3D