Little Johnny wanted to walk his dog. So he goes to his mom and asked, "Mom? Can I take the dog for a walk?" His mom replies, "No son, you can't." "Why not?" Little Johnny inquired. "Because son, she is in heat," she explained. "What does that mean?" he asked. Exasperated, and not wanting to reply she said, "Go and ask your father."
So he does and he asked his dad, "Dad? Can I take the dog for a walk?" His father said, "No son, you can't." "Why not?" "Because she is in heat," the dad explains. "What's that?" Not wanting to explain, the father rubbed some gasoline on the dog's rear end and said, "Here go ahead and take her for a walk."
So little Johnny took the dog out for a welk. Ten minutes later he came home without the dog! The father asked, "Where is the dog?" Little Johnny replied, "She ran out of gas a while back. Now another dog is pushing her home."