There is no widely documented single source for this clip, which circulates online as a short British reaction sound rather than a famous movie or television quote. Its appeal comes from the phrase itself, a polite British way of saying you cannot believe what you just heard, delivered here in a clipped, questioning tone. That mix of manners and disbelief makes it easy to reuse across memes, reaction videos and short-form edits, where a familiar expression can carry the joke without needing extra explanation.