Known as being empathetic, kind, and able to manipulate people via his famous puppy dog eyes, Sam Winchester is the smarter of the two Winchesters in terms of studies, even though he has refuted this fact.
At the beginning of the show, Sam is attending Stanford University as a pre-law student, which speaks to his intelligence for a kid who received a less than formal education.
By comparison to his older, more aggressive brother, Sam is often the exasperated voice of reason. He does not see monsters in black and white like Dean. He operates on an innocent until proven guilty basis.
However, don't let that big brain and kind eyes fool you into thinking he is nothing more than a bookworm. Sam has bested many great foes such as Lucifer himself, and has been possessed by both a demon and an angel simultaneously and still managed to live.
Sam has certainly been through the wringer in his lifetime. His mother was killed because of a demon deal to save her husband that allowed the demon Azazel to come into his room while he was a baby to turn him into a human-demon hybrid that gave him special powers. But, it also made him a target for angels and set him on a course that led to his possession by Lucifer and demon-blood addiction that caused extensive rifts between his brother and him. This is just the tip of the Sam Winchester iceberg.
"What kind of house doesn't have salt? Low sodium freaks." - to Dean as they scrambled to use salt against a ghost in episode 1x19
Sam and Crowley, formerly the King of Hell, have quite the tumultuous relationship. While they have worked together in the past, mainly out of necessity and desperation, more often than not Sam has tried to kill Crowley.
The Ruby Controversy of seasons 3 and 4 have made Sam suspicious of any creature harboring black eyes (the demon trademark), and as such he holds no love or even begrudging respect of Crowley. In response, Crowley bestowed Sam with the affectionate nickname of "Moose," and it has become a fan favorite meme.
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Crowley: Makes your flesh crawl, doesn't it Moose? (talking about hell) I get it. I'm King of this place. It's still not my cup of tea.
Sam: I don't know Crowley. I'd say it suits you. Dark. Empty.
Crowley: Fascinating; the utter contempt, when I'm in the midst of saving the Winchester's bacon, again.
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Regardless of their love/hate relationship (mainly Sam hating Crowley and Crowley loving it), their dynamic makes for hilarious and drama-filled exposition.
Constantly mocking the brothers for their style of dress, i.e. their flannel shirts and dusty boots, Crowley prefers the finer things in life, such as fancy hotels, 200-year-old scotch, Armani tailored suits, and glorious torture while getting one-up on his enemies.
Crowley is a fan favorite, and the adoration the Supernatural fans showed his character made him a regular for more than 7 additional seasons.
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Coulrophobia, a fear of clowns, affects many people not only during childhood, but well into adulthood.
For instance, I myself have an intense fear of clowns. They're weird, always smiling (why are they always smiling? Like what is so funny that you have to constantly smile and laugh? Are you planning something sinister? I digress.) and it creeps people out.
For Sam Winchester, despite all the terrible nightmares he's faced and all the monsters he's fought and defeated, clowns scare the bejeezus out of him. (Can't say I blame him.)
In episode 14 of season 7, called "Plucky Pennywhistle's Magical Menagerie," the Winchester brothers roll into town due to a strange death- a man who was killed by a 30-foot octopus. They soon discover that the drawings of young children on the wall of Plucky Pennywhistle's Magical Menagerie (similar to our Chuck E. Cheese only worse) are coming to life and killing their parents. While investigating at the place of business, Sam is confronted with his lifelong fear of clowns. Each time a clown is nearby, you can see Sam Winchester, the vessel to Lucifer and hunter extraordinaire, visibly flinch.
In typical Winchester fashion, the two brothers split up to divide and conquer once they discover the suspect- a worker who was using witchcraft as a way to bring the drawings to life. Dean takes the human while Sam handles the clowns. It makes for an epic and side-busting hilarious showdown!
Click on the photo for more information on Coulrophobia or in laymen terms, the fear of clowns.