Inconceivable comes from Halo: Reach, the 2010 first-person shooter developed by Bungie for Xbox 360. The line is spoken by announcer Jeff Steitzer, whose medal calls have defined Halo multiplayer since the early games. In Reach the word rewards one of the highest spree medals, so most players rarely heard it in normal matches. Clips of the announcement later spread through YouTube montages, forums and soundboards, where it broke away from the game and became a standalone reaction for feats that seem too good to be real.