There was a bus conductor, and he was good at his job.

He worked at it for a long time, and after several years of this, he ended up getting really dissatisfied.

One day, he went into work, and the first person who asked him for money had 3 screaming children. They just wouldn't shut up, no matter what he did.
The next person didn't have change, and had to break a £20. By this point the Conductor was just fuming.
"One more person pisses me off today," he says "and I swear I'm going to slaughter the whole damn bus!"
Sure enough, the next person who he asks didn't have any money at all. He flipped, pulled out a machete, and killed everyone on board.

He was taken away, and the Judge, apalled by the severity of his crime, issues the Death Sentence.

So he lives in Death Row for a few years before finally being led to the Electric Chair.

The executioner asked him what he wanted for his last meal. "A green banana" says the man. So the executioner hands him a green banana. He very deliberately eats it, before being led away.
He straps him into the machine, and turns the electricity on. After a minute, they shut the machine down. The man is sitting there, completely unharmed. "Hmm... maybe the machine's on the blink. We'll try again tomorrow."

So the next day, they try again, and again ask him what he wants as his last meal. Again, the man asks for a green banana. One again, he eats it, they strap him in, and again, leaving it on for a minute, the man is there, completely unharmed.

This follows on for the next week, each time the man eating a green banana, then the electrocution failing.

Eventually they decide they're going to have to try the lethal injection.

This is going to be a different executioner, so the first executioner says to the man "can I just ask you one thing?"
"Sure" says the doomed man.
"What's your secret? What is it about the bananas that makes you invulnerable to electrocution?"
"Nothing," says the man "I'm just a bad conductor!"