The 'On That Day, Humanity Received a Grim Reminder' meme originates from the opening scene of the anime and manga series Attack on Titan (Shingeki no Kyojin). It captures the terrifying moment the Colossal Titan looms over the 50-meter high Wall Maria, ending a century of peace. The quote itself is part of a longer narration describing the fear and disgrace of living like cattle in cages. In internet culture, the template is used to represent an impending disaster, a sudden realization of overwhelming power, or the appearance of a massive, unavoidable problem. Creators often photoshop different characters or objects in place of the Titan to symbolize something 'breaking through' their defenses in a dramatic fashion.