A little girl asked her Mom, 'Mom, may I take the dog for a walk 
 around the block?' 
 Mom replies, 'No, because she is in heat.' 
 
 'What's that mean?' asked the child. 
 
 'Go ask your father. I think he's in the garage.' 
 
 The little girl goes to the garage and says, 'Dad, may I take Belle 
 for a walk around the block? I asked Mom, but she said the dog was in 
 heat, and to come to you.' 
 Dad said, 'Bring Belle over here.' He took a rag, soaked it with 
 gasoline, and scrubbed the dog's backside with it to disguise the 
 scent, and said 'OK, you can go now, but keep Belle on the leash and 
 only go one time round the block.' 
The little girl left and returned a few minutes later with no dog on 
the leash. 
Surprised,  Dad asked, 'Where's Belle?' 
 The little girl said, 'She ran out of gas about halfway down the 
 block, so another dog is pushing her home.'