You need two people to start with. Person 1 is on all fours (they will be the lawnmower). Person 2 is the person trying to mow the lawn.
Person 2 pretends to “start” the lawn mower a few times. Person 1 makes noises like a lawnmower that won’t start.
Choose some people from the audience to try to start the lawnmower. The lawnmower still will not start.
Choose one more person from the audience (New counselor or a camper who can take a joke).
He or she tries to start the lawnmower and it starts up. Person 1 roars like a lawnmower then Person 2 says “Thanks. I guess all it took was a big jerk!”