Reese: What are you doing?
Malcolm: Wait'll Mom sees what you did to my expensive microscope.
Reese: You don't have the guts!
Malcolm: Say you quit, Reese.
Reese: NO! You're gonna be totally grounded when Mom sees the beating you gave to me! Ahhhhh... (punches himself)
Malcolm: What are you doing?
Reese: (continues punching himself with blood gushing out of his mouth) Sucker!!
Malcolm: Oh, yeah! Oh, yeah!!! (breaks his microscope as Reese continues punching himself)