The 'Enemy spotted!' line comes from Team Fortress 2 (Valve, 2007), shouted by the Spy when he calls out opponents, and it spread far beyond the game through voice-command spam and highlight reels. Streamers began firing it as a joke alarm whenever something went wrong, and short-form editors adopted it as a ready-made tension cue. Because the original clip is barely a second long it slots into almost any edit, which is why it is still everywhere years later.