Author: slytherinblack and kissedbythegods, and thanks in large part to lea_ndra on the quotes section, and clex_monkie89 on the updated version.
Spoilers: For the first five seasons. I remain largely unspoiled for season six, and the information I have isn't relevant to this manifesto, so I won't be addressing upcoming episodes. There are, however, MAJOR spoilers for seasons 4-5.
Note: this manifesto is currently undergoing major updating. Parts may be missing or incomplete. Thank you for your patience.
"You know Sam and Dean Winchester are psychotically, irrationally, erotically codependent on each other, right?" - Zachariah, "Point of No Return"
The above quote is from an angel who is trying to get the third Winchester brother, Adam, to help with a plan against Sam and Dean. Throughout the series, Dean and Sam show that they need each other - neither functions very well without the other, and they function together as a unit much better than they ever could as individuals.
Dean is a typical bad boy, alluding to James Dean, or at least on the surface. (Later we learn he's actually named after his grandmother, Deanna.) He tends to hit on women a lot ("We're allowed to have fun, you know. That's fun," he says in reference to an attractive waitress.) He comes off as a bit of a rebel, and in normal society he would be considered odd or rebellious, the black sheep and the one you don't mention in polite company, but in the Winchester family, he's the good boy, the one who always follows their father's orders without question and didn't disappoint him. He appears to be a fairly simple character, who doesn't really like to talk about issues or have "chick flick" moments. However, after the first couple of episodes, Dean begins gaining some depth.
Much of Dean's posturing and personal trademarks are attempts to emulate his father, who was a very tough ex-military man. In early seasons he almost hero-worships John Winchester, though later on he begins to admit that maybe his father wasn't perfect - and neither was his relationship with their mother, Mary. "It was only perfect after she died," he says in season five in response to Sam expressing surprise at a fight Dean remembered between their parents. Dean's trademark leather coat, his taste in classic rock, and his black '67 Impala are all things Dean acquired from John Winchester. (In season four, Dean travels to the past with the help of the angel Castiel and it turns out he helps talk John into buying the car, instead of the VW bus Mary wanted.)
In episode nine, Home, we see the first glimpse of a more vulnerable Dean. He's extremely torn up about having to return the the home where Mary Winchester died. "I promised myself I'd never go back there," he said. A little while later, he calls their still-missing father to try to get his help, nearly in tears at getting the answering machine yet again. At the time of the episode's running, it had a very powerful impact to see Dean break down for the first time, something that didn't happen again until late in the first season.
Dean's driving purpose in life is to take care of his family - after season one when John dies, and before half-brother Adam is in the picture, this means Sam. It's especially so because Sam is younger and his job was to take care of Sam when Sam was growing up, and because John told him to do so. Dean has always known about the world of the supernatural, since he was old enough to remember their mother's death at the hands of a demon and John's subsequent research into what killed her. Sam, on the other hand, didn't know about this until he was nine, though he was smart enough to have a clue earlier. The demon seemed to be after baby Sammy and Sam had a lack of knowledge about the things that go bump in the night, which also may have contributed to Dean's protective, and sometimes overprotective attitude. And he was also the one to carry baby Sam out of the fire that killed their mother, on John's orders. While Dean also has a drive to protect the wider world, his first priority is always to Sam.
Wisecracks seem to be how Dean handles everything, but especially the things he's uncomfortable with. His response to Sam's precognitive abilities is constant wisecracking but his initial reaction showed the viewer that he's not comfortable with it at all (but then again, neither is Sam). He also tends to take jabs at Sam's book learning, which indicates to me that he feels a bit inferior to be the uneducated one. He is very smart - he turned a Walkman into an EMF reader - but sometimes it seems like he doesn't realize that. Sam usually gets stuck with the research side of hunting, which Dean doesn't seem to find terribly interesting.
Sam has experienced a lot of tragedy in his life, starting with the untimely death of his mother when he was six months old. His mother died above his crib, presumably attempting to protect him. Unlike Dean he has never had the chance to be a normal child, as his father began chasing supernatural creatures in order to find his wife's killer immediately after her death, before Sam was able to retain memory. It is implied in many places that the sole or at least main source of affection for Sam as a child was from his older brother, as their father was consumed by the need to hunt and kill until his wife's death was avenged. In "A Very Supernatural Christmas", a flashback shows John Winchester missing at Christmas time, leaving Dean to figure out how to "acquire" gifts for Sam (he stole them).
The death of Sam's mother and the obsession of his father seem to be the culminating reasons that Sam craves the normalcy of "ordinary" life. He leaves home at eighteen as many teenagers do, in search of a life outside of his "home" at college. His father tells him that if he leaves he is not to return, and Sam still makes the decision to become independent from the only family that he has ever known. It's worth noting that Sam is very smart - scored a 174 on the LSAT- and wants to go to law school at Stanford when he graduates as of the pilot. (In season five, he appears to have let this go as something not meant to be.) In "After School Special" we see a flashback where one of Sam's teachers spots his intelligence and tells him for the first time that it's okay to not want to go into "the family business."
While at Stanford, Sam finds a girlfriend - Jessica (Jess) - and at the end of the pilot episode she meets the same fiery death that his mother did, incinerating above his bed while he is lying on it. That moment can be considered the inciting incident in the Sam/Dean relationship, as Dean yet again becomes the only source of emotional support and love that Sam has access to. Much like his father, Sam becomes consumed with the desire to find the demon that killed Jessica (and possibly their mother, as well), and he agrees to join Dean on a quest to locate both their now missing father and the perpetrator of the deaths of the only women that have ever played significant roles in his life.
While Sam and Dean both represent literary archetypes, Sam appears to be the reluctant hero. He is, so to speak, the brains of the operation and the sensitive one. He is a dreamer. He tries to escape his destiny, only to be drawn back into the one thing that he had sworn never to do again. It is established quite early in the series that he is beginning to have psychic premonitions in the form of dreams, a gift that only proves handy to his destiny as a hunter.
As the series unfolds, Sam's character conflict begins centering on his desire for Dean to treat him as more of a partner and less of a little brother. Dean lives for Sam's safety, but at times tends to not treat him as a grownup capable of making his own decisions. This often expresses itself as Sam pushing Dean away and sometimes parting company with his brother in an effort to be his own person.
Sam also displays anger management and substance abuse issues. After the season three finale and Dean's death, it's implied that he spends most of his time heavily drunk until the demon Ruby finds him, at which point she gets him hooked on demon blood (sort of a supernatural steroid). His anger issues display as early as "Asylum" in season one, where a ghost gets him wound up to the point where he shoots Dean in the chest with rock salt for bossing him around during the episode. In late season five, it turns out that Sam and Jess were introduced by a demon working to insure that anger was maintained, because during his college years when things were going well he was starting to settle down. We also learn mid-series that in the pilot episode, when Sam's mother was trying to protect him from a demon, that demon fed Sam demon blood. The blood can impart a variety of powers; in Sam's case it first manifested as visions related to other children with demon blood and to the demon whose blood he was given. Later, when he starts drinking Ruby's blood, it mostly manifests as the ability to exorcise demons from their hosts.
The mytharc of Supernatural is ultimately about how Dean and Sam are descendants of Cain and Abel (Cain through Mary; Abel through John) and are destined to be the human hosts for Michael (Dean) and Lucifer (Sam). Their parents' romance was even orchestrated by the angels to help bring about Sam and Dean's existence.
Sam/Dean in canon: Who needs a fourth wall? We don't need no stinkin' fourth wall!
Sometime around the fourth season, Supernatural decided "hey, fourth wall? We don't need no stinkin' fourth wall." In episode 4.18, The Monster at the End of the Book, Sam and Dean discover that there's been a series of books written about them by a man named Chuck, who happens to be a prophet. (He's also widely believed to be a stand-in for Kripke, the creator of the show, and is later implied to be God's human form on earth.) Chuck's been having dreams about Sam and Dean and has begun writing them down and publishing them. The publication of the Supernatural books in the Supernatural universe corresponds to the first three seasons, after which the publisher went bankrupt.
After discovering the books exist, Sam Googles them (never Google yourself, Sam, it's a bad idea) and discovers fanfic. "They do realize we're related?" quips Dean.
Yeah, Sam/Dean fanfic is canon in the Supernatural universe. Wrap your head around that. It's also the only pairing acknowledged to exist in the fandom for the Supernatural books.
At the beginning of the fifth season, Chuck needs to deliver a message to Sam and Dean. He does so via a Sam/Dean writing fangirl he sends to meet them named Becky. Later on, it turns out that Chuck may have a bit of a crush on Becky and they start dating mid-season five. The creator of the show/God is dating a Sam/Dean fangirl. What are you trying to say there, Kripke?
In the same episode where Becky and Chuck start dating, we meet Demian and Barnes. Demian and Barnes are Sam and Dean roleplayers who also happen to be dating. This is probably as close as Sam/Dean can get to canon and still make it past the censors (and also not scare off the non-Sam/Dean fans).
-running joke about people mistaking them for lovers
Sam and Dean apart
They would do anything for each other
Because of what happened to Jessica and his mother, Sam feels guilty, and as though people around him keep dying, as he confesses in the episode "Hook". More specifically, it seems to be the women in his life that keep dying. It seems unlikely that Sam would allow himself to get close to another woman, or really anyone at all, for this reason.
This is where Dean comes in. Dean is "safe" because Dean knows how to take care of himself, unlike their mother or Jessica. As the older and more experienced one, Dean is usually the one to save Sammy from getting in deep with whatever creature's got him in the current episode, though occasionally Sam gets to rescue Dean.
These two have a complicated relationship, but that's part of what makes it interesting. Sam is jealous of what Dean has with their father. In some ways, there's a lot of built up resentment here. Sam hates that Dean is the default boss, as any good younger brother does. Dean hates that Sam ran out on them. Dean may also resent that Sam did have that normalcy, no matter how deep that resentment's buried.
Oddly enough, Dean is not entirely comfortable with Sam's new abilities. He seems to be mostly coping in the episode following Home, but his initial reaction was one of worry/concern/freaking out a little bit.
In The Journey Home, Sam encounters his mother's ghost. It wasn't really shown what effect this had on him, but since he didn't remember much of her up to that point, it probably had at least a little. Maybe it's the fact that Sam having supernatural abilities begins to make him similar to the things that Dean has sworn to hunt down and destroy.
But at the same time, Sam's all Dean has got, and since Sam's dreams literally burned to ash, Dean's all Sam really has, too. They were raised on the road and never really had a chance to develop normal relationships, and now that they're both constantly on the move again, they probably never will. Both of them, however, seem to need the other to lean on. Despite their differences causing sparks sometimes, they truly complement each other. When one gets in trouble, the other is always there to bail them out. Dean has a mental library of knowledge about the supernatural, but Sam has the technical know-how of how to do library and internet research. Dean's a smooth talker, but Sam is naturally the sort of person you trust your secrets to. Dean acts when they need to, and Sam thinks when they need that. Watching the show, one can tell that they work together perfectly, watching each other's backs.
In conclusion: Why we ship it
Well, for one thing, it's hot. [g] Just look at those two. This pairing has everything I look for in a couple. It's angsty, it's twisted, they have as many issues to work out as the middle east (my apologies to the middle east and the analogy police). But despite the problems, they're each all the other's got (well, Dean's got a car, but in terms of worldly possessions and long standing relationships, neither of them is exactly rich). Every time one of them gets into trouble, you can see the other one worried to death about it. The levels of emotion between the two in the series are amazing.
Also, Sam's the only one allowed to touch Dean's car. (No, that's not a metaphor. But it could be.)
Point of No Return</b>
Sam: I swear man, you gotta update your cassette tape collection.
Sam: Well, for one, they are cassette tapes, and two... Black Sabbath? Motorhead? Metallica? It's the greatest hits of mullet rock!
Dean: You know house rules, Sammy. Driver picks the music, shotgun shuts his cakehole.
Sam: You know, Sammy is a twelve year old chubby boy. It's Sam, okay?
Dean: [cranks up the volume on the radio] Sorry, I can't hear you! The music's too loud!
Sam: What were you thinking shooting Caspar in the face, you freak!
Dean: I saved your ass.
Sam: Dean, what I said about Mom and Dad, I'm sorry.
Dean: Hey, no chick-flick moments.
Sam: All right. Jerk.
Cop: Is there anything about you that's real?
Dean: My boobs.
(after a villian stole Dean's car)
Dean: ... the thought of him driving my car...
Sam: Dean, come on!
Dean: It’s - killing me.
(Sam and Dean investigate strange accidents happening on a building lot. Sam and Dean introduce themselves to Larry, the salesman selling the houses.)
Larry: Let me just say... we accept home owners of any religion, race, color or... [meaningful pause] - sexual orientation.
Sam and Dean: ...
Dean: ...we're brothers.
(Later they meet Larry's assistant, Linda)
Linda: So, you two want to become homeowners.
Linda: Let me just say, we accept home owners of any race, color, religion, or... sexual orientation.
Dean: I'm gonna talk to Larry, okay, honey? [slaps Sam's ass and walks off]
Sam: You're my brother and I'd die for you, but there are some things I need to keep to myself.
Dean: [when Sam's filming him on camera to test it] Do I look like Paris Hilton?
Dean: [to Sam] So who's the hotter psychic: Patricia Arquette, Jennifer Love Hewitt, or you?
Dean: [desperate, defeated tone] If you hurt my brother, I'll kill you, I swear. [angry] I'll kill you ALL!
More quotes provided by wistful_fever and can be found here. Also see sn_quotes
http://craftymonkie.com is the source of all screencaps, including the ones I used.
There is an insane amount of stuff out there at this point, guys. The list below is from the original 'manifesto, but at this point I couldn't even begin to point you to all the stuff worth reading, if this is your thing. I definitely suggest checking out Crack Impala's weekly Sam/Dean recs, or spnfencentral or spnroundtable, both of which do regular rec lists. And the Sam/Dean tags on delicious are also a good way to go.
And the great genderbending sequence by three different authors: Man, I Feel Like a Woman; That Old Slippery Slope, and Opportunistic Lover.
The Rules Remain a Mystery
Those are my absolute favorites, but 90% of the fics I've seen are just excellent.