The meme comes from Among Us culture, where “sus” became shorthand for suspicious during the game’s huge online popularity in 2020. The phrase “when the imposter is sus” spread widely through YouTube, TikTok, Discord, and remix edits, often paired with a shadowed emoji or exaggerated close-up. Rather than pointing to one single official source, most people know it as a community meme built from Among Us jokes. It remains popular because the setup is simple, flexible, and instantly readable in short-form comedy videos.