I know this isn't what actually happens in the series, but I wrote this a long time ago (right when Cas left in fact), and I thought I might as well post it.
Castiel landed in an empty field for the first time since returning to heaven.
Being on Earth as an angel was much different than being on Earth as a human. He'd almost forgotten the sensations.
In this field he could feel the life flowing through all the creatures present. The bees busy pollinating flowers, the ants crawling amongst the blades of grass, the worms moving through the soil beneath his feet.
Castiel closed his eyes and let the life of the place wash over him.
Once he felt he'd regained a little of his acquired humanity, he opened his eyes, spread his wings, and flew.
He wasn't quite sure where he was going, and he quickly lost track of how long he'd been flying, completely distracted by the rush of wind across his wings.
When he began to tire, he landed and took in his surroundings.
He frowned in confusion. He recognized this place. This was familiar.
His feet began to move before his head caught up, and he found them leading him along twisting streets, beneath bridges, and across rivers, until he stopped at a small run down house on the outskirts of town.
Castiel could feel a presence behind the door; a familiar presence. He reached out a hand for the doorknob and jerked back, as though burned.
Castiel's head fell to the side, and he looked at the house once more, this time a little… deeper.
Radiant blue symbols shined back at him in intricate patterns that clearly indicated that he was not welcome here.
Fondness tugged at Castiel's heart.
With a smile he reached out a hand and tried the human way, pushing a small white button beside the door and listening to the echoing tinkle of tiny chimes.
The presence within the house did not move.
Castiel frowned and pushed the button twice more.
The presence grew agitated and moved further away, deeper into the house.
Castiel scowled, and briefly considered letting his newly restored grace shake the buildings very foundations, but knowing his lover, that would just make him run and Castiel really didn't feel like chasing him right now; Crowley could be a sneaky bastard when he wanted to be.
Castiel raised a fist and beat a harsh staccato rhythm into the wood, ringing the doorbell again for good measure.
He heard an explosive shout echo from deep within the house, and then he was awash in an incredibly hot wave as Crowley cursed him.
Castiel waved his hand and it passed. He knocked again. Louder.
The presence stilled instantly. Castiel knew his lover was staring at the door incredulously, and he couldn't stop the smirk that crossed his face.
Then it was moving swiftly towards him; the door was ripped open, and he stared down the barrel of the colt.
Castiel's head fell to the side. "Why do you have that?"
Crowley's eyes widened dramatically, and the gun lowered in shock. "Uh, I'm… borrowing it. What are you doing here?"
Castiel smiled, and leaned as far forward as he could, pausing only when the invisible barrier stopped him. He pressed a soft kiss against it, and leaned back.
Crowley was gaping at him.
With a few quick gestures, the demon destroyed all the angelic barriers, and hurriedly pulled Castiel inside, slamming him up against the door. "Thought you weren't coming back."
Castiel threw his head back, baring his neck; the demon moved in to lick and bite at it. Castiel grabbed at Crowley's hair. "I came back as soon as I could."
Crowley bit Castiel's shoulder hard enough to draw blood; he licked at the wound until the skin healed. "Good boy."