Frank Miller, who plays the mission control voice, was a member of the U.S. Air Force in reality, and a real mission controller. He was hired because his voice was the most authentic the producers could find for the role. Inexperienced and nervous, he could not keep from tapping his foot during recording sessions, and the tapping sound repeatedly came through on the audio tracks; Stanley Kubrick folded up a towel, put it under Miller's feet, and told him to tap to his heart's content.
