Do you think Constantine might hold a little grudge that NBC only gave him one season before canceling his show? On the “Haunted” episode of Arrow, Constantine took a little dig at his former network.
One of the items that Constantine had Felicity bring him in preparation for attempting to restore Sara’s soul was a dead peacock feather. Felicity was confused over why Constantine would need a dead peacock feather. It turns out Constantine didn't need the feather for Sara at all. Constantine took the feather and simply used it to scratch an itch on his back. Nothing can be more satisfying than scratching an itch with a dead peacock feather.
Of course, NBC is known as the Peacock Network because of their Peacock logo, which they started using in 1956.