Pas mal is a common French expression meaning not bad, and vestiaire means locker room or changing room, so the phrase works like a dry approval of a space. The clip circulates as a short French meme sound rather than a widely documented quote from a film or show, shared in edits about sport, school, gyms and group hangouts. Its humour comes from treating an everyday room like a professional team facility, which is why it still fits reaction videos, football edits and ironic room tours online.