When Homer and Marge are going on a ride (forgot what for -- I think a fridge motor) they stop at a barn. 2 pigs run by, named Steve and Theresa. :) The barn owner sees the door open and goes to find the tresspasser. You will notice that the door is open. HOW ELSE WOULD THE PIGS GET OUT? Then, when they show the inside of the barn, the farmer is struggling to OPEN THE DOOR! Well, there is only one thing I can think of that closed the door... the wind.