When I stick my right elbow in my left ear, i shock the dog.

I was having trouble driving a Darlington transistor using my DAQ board. I had wired a simple LED test circuit, but things just weren't working. It turns out, I had completely screwed up the polarities by confusing the conductor direction on the bread board. The LED would light when I touched the negative lead to the positive post.

"What have you done?" I wondered, "What have you done?"