In 2003, two overweight teenaged girls decided to sue McDonald’s because of their rapid weight gain. The argument they created was:
McDonald’s food is fattening
These girls are fat
Therefore, McDonald’s made them fat.
The form of the argument is valid because it follows the proper form of an argument and it is factually correct therefore it is also sound. The argument that the girls are presenting is very irrational because McDonald’s did not force these girls to eat their food. It was their personal choice. Of course the case was dismissed because of how far fetched the accusations were.