The line comes from Fire Emblem Radiant Dawn, the Nintendo Wii strategy role playing game released in 2007 as a sequel to Path of Radiance. In context it is a quick, dismissive explanation meant to end suspicion and move the scene along. Clips of that exchange later circulated outside the game as a standalone reaction, because the excuse works in almost any situation where someone is pretending nothing happened. Its deadpan tone has kept it useful for gaming edits, memes, and false alarm jokes long after release.