Crowley plays a key role on the Supernatural episode "Two Minutes to Midnight." In this scene from it, he makes Bobby admit something major to Sam and Dean.
The season finale of Supernatural is creeping closer, and this episode takes a major step in that direction. It features a dangerous deal for Dean and is titled "Two Minutes to Midnight."
The demon Crowley reveals something important to Sam and Dean on the episode "The Devil You Know." He tells them how he's been able to track Sam and Dean.
Why do they call this place The Empty? It's full. It's full of sorrow and despair playing over and over again of angels and demons dreaming about their regrets. Forever.