It's been a long trip. The hunt you were on wasn't particularly difficult but things had gone wrong, as they always seem to do when the Winchesters are involved. The pair of angels on Cas' trail were not much of a problem but their buddy hiding under the stairs made things complicated. You had taken out Stunt Angel #2 with an angel blade, only to get jumped by some lousy broad in a bad polyester, Avon lady suit. Deflecting the attack from a blade of her own, she sliced up your forearm like a chuck roast. Cas ganked her with lightning speed while Dean easily handled the other one. They had a few cuts and scratches. You had a deep gash from the inside of your elbow to your wrist and it was gushing blood. Dean made a fast tourniquet out of his bandana and they hauled you to the emergency room.
Sitting in the passenger's seat of the Impala, leaning your head against the cool glass, your arm is killing you but you don't care. They gave you enough morphine at the ER to take down a small elephant. Cas had offered you the back seat but you declined, deciding that sitting upright might avoid any accidental pressure on your injured arm. So he was snoring softly, mumbling something about pickles every now and then.
After finally finding a comfortable position, you were drifting off when Dean hit a pothole and you banged your head against the window.
"Crap, Dean," you cursed, "I was almost asleep."
He was chucking as you rubbed your forehead. "I'm sorry. Not a good idea to lean on the glass while the car is in motion. These shocks aren't the best."
"Tell me about it," You grumbled, "I can't lean my head back either. My neck gets so stiff." Your words are slurred and you come off like a petulant child.
"Come 'ere," he says softly.
"No," you reply as you yawn loudly and Dean pulls you across the bench seat.
Dean chuckles again, "Stop being so stubborn. Lay your head in my lap. You will be more comfortable." His eyes are sincere and caring.
"Ok, but no funny business, Mister."
He outright laughs, throwing his head back as you lay your head over on his leg. His body is warm and comforting. You shift positions to get comfortable which results in you lying fully in his lap, staring up at him. The shadows of the occasional street light pass across his inhumanly beautiful face.
"God, you are handsome," you mutter.
Dean gives you a half grin, "Yeah, I know. Rest, ok?"
You nod and close your eyes, letting the pain medication take you away. You drift off to sleep to the sound of him humming "Ramble On" and gently stroking your hair.
Based on an imagine submitted by me to Supernaturalimagine .tumblr .com. (no spaces) "Imagine falling asleep in Dean's lap while he's driving the Impala"