The line comes from Stanley Kubrick's Full Metal Jacket (1987), spoken by Private Joker, played by Matthew Modine, during the film's battle sequences in Vietnam. It riffs on the way classic John Wayne war films sold a heroic fantasy of combat that bore no resemblance to the real thing, which is why it became one of the film's most quoted moments. Decades later the clip resurfaced on meme soundboards, where creators use it the way they use other movie reaction staples like It was at this moment he knew, as shorthand for a moment when reality stops making sense.