When I was in early grade school there was one substitute that was beloved by all the students. When the first day of school came around for 5th grade my class was delighted to learn she was now going to be our full time teacher. It was a great year.
I think it was 8th grade and there was a sub, I think may have been on her very first assignment. I had never witnessed a teacher lose such control of a class before that, or since. There were kids on all fours crawling around the floor barking like dogs, things being thrown about, and a noise level that made normal level conversation impossible. We never saw her again.
About the worst thing I did when there was a sub was talk to the other kids, just like everyone else was doing.