He is Minion of Bowser. He is kind of magikkoopa.
After beating bowser in Peach`s Castle grounds he say:
"I helped you save Mushroom Kingdoom; however, that doesn`t means we are not enemies"
He gives you Green Sunshine from Goomboss and Red one from Big Bully.
He never kill you himselve.
Ripped from Yoshi`s Island SMW 2.