The phrase is French for the mutants are falling back asleep, and the clip circulates online under that exact title as a short reaction sound. Its origin is not clearly documented, so it is shared mainly for the deadpan delivery and the oddly specific wording rather than a known scene. Creators reuse it in edits, streams and group chats whenever activity fades, treating the line as a mock announcement that whatever was stirring has settled again, which keeps the joke understandable even for viewers who do not speak French.
About this sound
A short French voice clip saying les mutants se rendorment, used as a funny reaction when a group goes quiet, powers down or falls back asleep.
This short clip features a calm French voice announcing that the mutants are falling back asleep, delivered in a flat, matter of fact tone over less than two seconds. The humour comes from the contrast between the dramatic word mutants and the sleepy, anticlimactic ending, as if a dangerous threat has simply switched off. It lands like a narrated caption for a sudden lull, turning silence, inactivity or a failed attempt to get going into a small story with a beginning and an immediate, drowsy end.