top ten ways dean proposes to cas after he returns from the empty (companion to this post):
he buys a set of wedding rings while cas is gone. the main idea behind that purchase is so that dean can wear a visual reminder of what he's lost. cas' ring is an afterthought but when cas comes back, dean is really glad he got them both. he doesn't even say anything, just takes cas' hand and slides the ring on his finger
during movie night, a week after cas comes back and six days after dean tells him he loves him too. they're watching dirty dancing and during the dance scene at the end, dean jokes that cas could probably lift him one-handed. cas says he could, if dean wanted, and dean just looks at him and blurts out "will you marry me?"
he plans it for weeks. agonizes over it. nothing he can think of feels good enough, not with everything cas has given him, and finally, in a fit of frustration, he stalks up to cas in the kitchen and demands "so will you marry me or not??"
he asks jack for his blessing first. jack looks at him, confused, and says "i thought you were already married?"
they've been dating for about two months when cas has a near death experience on a hunt. they retreat to their motel room afterwards, cas a little bit rattled but otherwise no worse for wear, and dean tells him this is it. no more hunts. cas says mildly that if that's all it took for dean to consider a less dangerous lifestyle, he would have done it long ago. dean tells him to shut up, he has done this before, and every time it makes dean want to die. "but no more. we're gonna do the retirement thing and get real people jobs and get married and you're gonna be safe."
he asks sam for advice. sam looks at him, confused, and says "isn't this a bit soon?" "i've been in love with the guy for ten years, sam, how much longer should i wait?" "ten years??"
he takes cas on an evening drive. parks in a scenic spot, sits with him on the impala's hood. they watch as the sun sets and the stars come out. the radio is softly playing in the background. it's the romcom moment right out if dean's most secret dreams
he buys the ring and tosses it at cas before he can think twice. "is that-?" "you gonna put it on or not?"
after dean has a near death experience. cas is furious and worried out of his mind, berating dean for not being more careful, and all dean can do is look up at him in a daze and ask "will you marry me?"
they've been together for years when one day dean looks at cas from across the breakfast table and asks "why aren't we married yet?" and cas puts his cup down and calmly says, "would you like to rephrase that question?" and dean blinks. smiles. takes cas' hand, squeezes it tight, and says, "sweetheart, will you marry me?" cas says yes
(every single time, cas says yes)
