Krark, that guy with the thum

The first time you would cast a instant or sorcery spell on each of your turns, before it's revealed, choose an opponent. That player chooses to counter that spell or create a copy
they may cast without paying it's mana cost (the spell is cast and put into exile facedown until opponent chooses counter or copy, only then is it put onto the stack)
Partner with bill the thumb salesman