I paused for effect. What I'd expected to happen occurred. The people seated around the room shot glances at one another. It should be thrown with great force. Probably the second most common element of humor is superiority.
People like to feel that they're somehow better than everybody else.
Let's make the people in the other rooms think they picked the wrong session to attend. You pay him for the pizza. In order for humor to be effective, it must serve a purpose. Sometimes that purpose is nothing more than a welcome break from the routine. Other times the purpose is to stress a point.