Automated dialogue replacement

The performer watches the take and delivers the line again in sync with what is on screen, recorded somewhere quiet. Film crews do this for scenes ruined by wind, traffic or a camera motor. Creators run a smaller version constantly: a fluffed sentence, a microphone that was off, a word that needs changing after the fact. Two things make it work. Match the sound of the original room, because a clean voice dropped into a live-sounding scene stands out immediately. And match the energy of the take. A technically correct, flat replacement is more obvious than the noise you were trying to fix.