phrase originally coined by borat
to express his pleasure at the supposed opulence of his hotel. in the vernacular, the phrase is generally meant to refer to a person who has attained great success
in his life
Person A: Dude, I fucked Anna last night."
Person B: "Anna? She'd never fuck you. You're shitting me, right?
Person A: "Nah, dude; king in the castle."