And also, I don't really think it matters, but

Is also a boss. He is Gon Ga Jora from Mario RPG 3.
This is the cutscene.
Gon Ga Jora (I'll call him Gon): Welcome, my friends. I see you have brought the Beanstar back to me.
Mario & Luigi: Ooh Yeah! *Nods*
Prince Peasely: Yes, sir. We wouldn't leave you even if we were dead.
Gon: (Eyes glow red) Well, yes. *Eyes the Beanstar*
Prince Peasely: Isn't that right, Mario Bros.?
Mario & Luigi: Oh Yeah! *Spins around*
Peasely: NO! DON'T!!!
*The BeanStar goes flying into the wall. A purple gas spreads out, Evil music plays*
Mario: AAAAAAAH!!!
*The BeanStar splits into four pieces and fades away*
Peasely: NO! The BeanStar!
Luigi: *Cries*
Mario: NNNNGH!!! *Slams Luigi into the ground with a Hammer*
Peasely: Don't worry, sir! We'll recover the pieces!
Gon: NOT BEFORE I KILL YOU FIRST!!!
Cackletta: *Appears from the Purple Fog* EYYAHAHHAAHAA!
Gon: Take this, Green Bean!
*Prince Peasely goes flying- Mario Bros. Start panicking*
Cackletta: *Flies into Gon's Mouth*
Gonletta: !AND TAKE YOUR WORTHLESS EXISTENCE WITH IT, MARIO BROS.!
*Becomes Huge, Bends over and breathes fire*
*Final Boss Battle Begin*
Yep.
