I knew when they started watching a YouTube video about a cat, all would be chaos. And so it was...but it was fun and the point was how to embed the video into a Prezi. They got it.
It's ok to get rowdy once in a while. I would not recommend it for every single time you stand in front of a class or a group of people you are training, but now and then a little rowdiness is good for the soul. We should never forget how to play and have fun, even as we work to learn and teach.