So sometimes I think about Dean opening Sam's laptop for... research. Yeah, that's what it is. But now it has this little box that asks Dean for a password. Shit. Sam was always a quick learner, and he probably didn't like what he found on his laptop the last time he let Dean use it. Dean lets out a sigh and tries all the things he knows Sam likes: "dogs", "salad", "Stanford". As these don't work he tries Sam's birthday and some of those bands he remembers on his iPod and some random things that spring to mind like "Jessica" because he's getting desperate. The entire time he's grumbling about his geek brother probably using some lawyer guy's name he learned at school. Or maybe Cas taught him something in Enochian. Or maybe the laptop has some kind of high-tech finger scanning thing he really can't break into even if did figure out the damn password. Dean finally gives up, because Sam is going to come back soon and it's not worth it.
When Sam comes back and pulls out his computer, Dean has a plan. He offers Sam a beer to give him an excuse to pass behind him at the perfect moment. Sam accepts the offer, so as Dean is walking towards the mini-fridge, he turns his head just so and his eyes focus on the screen as it flickers on and that box appears. It takes Sam less than a second to type it in, and Dean has to stop in mid-step so he can see it.
The password is four letters: "Dean".
But that awkward pause gave Dean away, so Sam rolls his eyes and yells, "seriously, Dean?" and he immediately opens his preferences to change his password. Well, that didn't work. Dean frowns and considers his other options. Maybe Sam will tell Kevin the new password. Or maybe Charlie will let him use that tablet of hers...
And once Dean's focused on the fridge, Sam closes his preferences window without saving the changes.