Enter scene. Two or more characters talk for a while. They say things which aren't funny. Background laughter. All present pause while the background laughter is on. Resume talking. Somebody will use a joke that was once funny in 1953. Background laughter again. Resume talking. Some physical bit of comedy will be used. Nobody will laugh at home. The audience will split their sides. Like before, everyone will pause for a nanosecond while the background laughter plays
Enter scene......
Enter scene......