The line comes from Regular Show, the Cartoon Network animated series that ran in the 2010s following Mordecai and Rigby, whose exaggerated reactions made the show a steady source of meme audio. Short outbursts like this one were clipped by fans and passed around on soundboards, where they became shorthand for moments of stunned disbelief. It endures because the phrasing is universal, fitting anything from gaming reveals to real-life surprises, and because the frantic cartoon delivery reads instantly even at just over a second long.