If you know where this joke came from...well, you're pretty cool.
Two inmates escaped from the asylum, and found themselves on the roof. They needed to get to the next roof be free. The first inmate says to the second, 'I'll turn on the flashlight, and you can cross over, and I'll follow.' The second inmate looks at him and says, ' Do you think I'm crazy? You'll just turn it off when I'm half way across."