Put it immediately after the reveal in a prank edit, before a shocked sound, then close the scene with an oh no no no laugh once the reaction has landed.
À propos de ce son
This is a short Russian voice clip saying 'a my i ne dumali', meaning 'and we didn't even think', delivered in a flat, matter-of-fact tone. It lands as a deadpan shrug, funny because it sounds like a calm denial after something has clearly gone wrong. It works best as a quick spoken reply when a plan falls apart.