I think hungover Dean is hard to resist for cutes. So adorably rumbled compared to his normal preening. Shuffling around in his socks with his hair all askew and blinking blearily at everything around him.
I originally headcannoned that Dean stole that pair of jeans from Sam… then neon reminded me that in my story my headcanons are canon, so Dean snitched those jeans from Sam, and they’re so comfy he uses them at night when he’s asleep! They’re too long for his shorter legs, so they bunch up around his boots if he wears them during the day.