Dean makes little stretching movements as he's driving. Movements that signal that he's getting tired, or has simply been sitting too long in the same position. First, the neck stretch, rolling his head to each side. Then the shoulder hunch and roll. He flexes his fingers around the steering wheel.

All of these things Sam sees, while pretending that he's still asleep, sitting side-on in the passenger seat with his cheek resting on the leather back rest. His eyes are open to mere slits, ready to close quickly if Dean should look over to him. Dean stills again and they drive for another few minutes before he clenches his buttocks and lifts his hips, no doubt trying to rid himself of a numbing ass. The movement is not lost on Sam. In fact, he quickly realises that he's going to have to move in the next thirty seconds due to his growing erection, and the fact that Dean will be able to tell, if he happens to look at his crotch. And why the hell would he do that? Relax. I'm the one with the inappropriate brother fantasy, not Dean. Dean would just think that I'm having a really good dream. Not that he'd look, anyway. He decides not to move; he'll risk it, just so he can keep watching.

A thought comes quickly to Sam, and it develops before he can stop it. Feeling a little reckless, he closes his eyes, shifts a little on the seat with a quiet, throaty moan, and repositions himself with his hand. Then, with a sigh, he settles again, hoping that Dean is buying his Sam's-having-a-horny-dream act. He pretends to sleep for another few minutes, and then – with his head still side-on against the back of the seat – slowly opens his eyes to look at Dean. If Dean is looking at him, he can just pretend that he's waking up, but Sam will catch him looking. He is a little disappointed, as it turns out, to find Dean concentrating on the road. He continues the charade of waking up, and sits up, blinking.

Dean looks over and then back to the road. "Nice dream?"

"What?"

Dean smiles. "You heard me, Woody Woodpecker."

Sam follows Dean's eyes down to his crotch. He schools his face quickly to a frown and a slight embarrassed expression. "Whatever." When Dean chuckles and turns back to the road, Sam allows himself a secret smile. So he did look. What does that mean? Covertly, Sam's eyes trail down Dean's body and he raises an eyebrow. Okay, big brother, I know the reason for my hard-on; what's your excuse? Sam allows himself only a few seconds to hope that it was in response to his little show. When he mentally shakes himself out of that self-destructive thinking, he fidgets a little on the seat to get comfortable.

Dean notices, and assumes it is due to his 'predicament'. "Dude, do I have to pull over so you can take care of that?"

Sam looks at him with a raised eyebrow and the hint of a smile on his lips. "Don't stop on my account. If you need to stop, though, you go right ahead." When Dean turns to him with an incredulous look, Sam smiles. "Looks like I'm not the only one who's been thinking happy thoughts." With that, he looks down at Dean's bulge.

Dean looks back out through the windshield, a little panicked. Then, realising that Sam would never guess why he was hard, he slips back into his regular banter. "Yeah, well, I had a pretty wild dream myself this morning, before you woke me up."

"Yeah?"

"Yeah. Gorgeous brunette with long legs, magic hands, and a wicked mouth." He grins at Sam, for effect. You don't need to know that the gorgeous brunette was you, Sammy.

Sam manages an indulgent smile in return, although he finds himself jealous – again – of another nameless, easy woman in a random town somewhere behind them. Moving positions again brings back their previous subject. "Sure you don't need to stop, Dean? It's probably gonna be a while before we get to Montgomery."

"About two hours, actually," Dean answers. "Passed a sign a couple miles back."

"Two hours is a long time."

"If you can hold out, I can, too."

Sam sinks his teeth into his bottom lip to stop from smiling. "What if I can't?"

Dean glances over at Sam. "What?" He says, surprised.

"What if I can't hold out?"

"You're kidding!"

"No," Sam answers with a straight face.

"What are you, fifteen?"

Sam shrugs.

"You seriously want me to pull over so you can walk behind some trees and jack off?"

"Would you prefer I did it in the car while you drive?"

"You can't be serious!" Dean says, his voice rising, not knowing whether to laugh or panic.

Looking at Dean's expression is too much for Sam, and he finally breaks into a huge grin and laughs.

"You bastard," Dean says with feeling. Although he wants to lean his head against the steering wheel and sigh with relief, he holds on to annoyance instead. "I'm gonna get you for that."

Sam, still feeling a little reckless, baits Dean. "Bring it on, tough guy."

"When you least expect it, Sammy."