Originating from the opening sequence of the Nickelodeon animated series Avatar: The Last Airbender, this phrase is part of Katara's narration describing how the 100-year war began. The quote, 'But everything changed when the Fire Nation attacked,' serves as a dramatic turning point in the series' lore. In meme culture, it is used to humorously signal a sudden, drastic, and often catastrophic shift in any situation—from a group of friends falling out to a sudden software update ruining a workflow. The template typically contrasts a state of peace or normalcy with a disruptive force, perfectly capturing the melodrama of unexpected life changes.