A class trip to the farm may seem boring, but not when Jimmy decides to bring out his boa constrictor to meet the other animals.  The farm gets completely out of control when each event leads to an even crazier event.  The out of control trip includes eggs getting thrown, pigs getting on the bus, the the boa eating the laundry off the line.  The humorous chain of events could work as an introduction to Newton's third law.