A man calls the Animal Control in his town, because there is a 
 crazed gorilla on his roof, and he can't figure out how to get it
 down safely.
 
 Soon after, a van pulls up, and an old man gets out, carrying a 
 small dog, a baseball bat, and a gun. He hands the man the gun.
 
 "Okay, here's what we do. I'm going to go up onto your roof, and 
 threaten the gorilla with this baseball bat until he loses his 
 balance and falls down." 
 
 "When he falls down, Spot here will bite him in the balls until 
 he's incapacitated."
 
 "Great," says the man. "But what's the gun for?"
 
 "In case I fall down instead of the gorilla -- shoot the dog."