The exact original recording behind this line is not widely documented, so online it is best understood by how creators use it rather than by a single film or show. The phrase is a familiar English exclamation of disbelief, and the clipped delivery makes it easy to drop into short videos where a longer explanation would slow the joke. It fits alongside other short reaction clips like Oh Brother, This Guy Stinks! and Owen Wilson Wow, which creators also use to punctuate disbelief. Its staying power comes from that directness: the question is instantly understood, even out of context.