4+ Kids. The last kid delivers the punchline.
An invisible bench in a park, or at a campsite.
The first person is squatting as though sitting on an invisible bench. A second person comes in and asks what the first is doing.
First Person Answers: “I’m sitting on the invisible bench”
Second Person Asks: “Can I join you?”
First Person Answers: “Sure, there’s plenty of room”
The second child squats next to the original person, pretending to sit.
A third person comes along, and the scene repeats.
Go on for as many children as you want.
When the last person comes along, asks and is answered with “We’re sitting on the invisible bench”, he/she says “But I moved it over there this morning!” (pointing across the stage).
“AAAAHHHHHH!!!!” and all seated kids fall down.