Parodied mercilessly when it's discovered that Bobby made a deal with Crowley, a demon who's been helping them. When Sam asks if they kissed, Bobby denies it, at which point Crowley clears his throat and shows the latest picture on his camera.
Mainlining the Monster: Sam did this a bunch of times with demon blood. Sam used it during the season 4 arc to enhance his psychic capabilities to be able to remove a demon possessing a victim without harming the host. He then becomes somewhat addicted to the substance, even keeping a victim possessed so that he can "bulk up" for the final fight.
Major Injury Underreaction: Lucifer, after being shot in the head by the Colt, the series until-then kill-everything weapon, crumples to the ground...before taking a deep breath and staring back up at Dean.
Male Gaze/Female Gaze: An odd one, this. There's a hot girl every episode and lots of attention gets paid to her cleavage, of course, but there's been slow, lingering shots panning up the boys' long legs and arses, half of their promo shots for Season 2 consisted of hooker poses and you just can't deny that they're not wearing a bit of lip gloss and eyeliner in Season 1 episodes. When there's a sex scene, the camera generally spends more time looking at Sam or Dean than his partner.
Mama Bear: In episode 8x02, Mrs. Tran is willing to sell her soul to the god of greed to save her son Kevin.
A Man Is Not a Virgin: Dean, although it's portrayed as not always a good thing. Hilariously, he concludes in Season 4's "Monster Movie" that, thanks to full body regeneration after being pulled out of Hell, he is a virgin again. (By the end of that episode he's not.)
Manly Men Can Hunt: Obviously Sam and Dean share a background, and they both "hunt" (demons) but manly Dean who accepts his blue-collar roots can not merely fix but rebuild cars, while Sam who went to college and wanted to be a lawyer (and whose masculinity Dean likes to make fun of) isn't allowed to drive any more and does not know how to do anything similar.
Manly Tears: You have to admit, they cry a hell of a lot for two, supposedly manly, blue-collar soldiers/warriors.
For its infamously poor treatment of female characters, the series' frequent depiction of male protagonists feeling and acknowledging severe emotional pain and distress without degrading their masculinity or playing it for laughs is refreshingly progressive.
In an alternate timeline in one episode, Bobby is married to the long-dead Ellen. They're cute together.
"The French Mistake" uses the "wedding photo" method to demonstrate that Jared Padalecki is married to Genevieve Cortese, the actress who played Ruby 2.0
Mars Wants Chocolate: Downplayed, where the Grim Reaper (who notes that he does visit alien planets) decides to ignore Lucifer's orders to wipe Chicago off the map and killing millions more during the Apocalypse. One of the reasons he gives for this is that he likes the city's pizza—this Death is a fast food junkie.
Sam is stuck in one in the season 6 finale of Supernatural after Castiel destroys the mental barrier that is keeping his traumatic memories from potentially turning him into a vegetable.
Dean and Sam also enter Bobby's nightmare world in another episode.
Mercy Kill: While soulless, Sam encounters five men who are All Webbed Up and infected with venom by a spider demon. Instead of taking them to a hospital, he arbitrarily decides to shoot them to spare their agony, then burn the bodies. Unfortunately the spider demon was actually creating more of itself, and the result is Immune to Bullets and fire. One of the victims, an ally Sam used as The Bait to find the demon, survives and wants revenge. He points out that rather than sparing him, Sam has actually created more monsters.
Merger of Souls: Castiel became something far more powerful by absorbing the souls of Purgatory. Unfortunately one set of them was too powerful for him and took over.
Metallicar Syndrome: The Impala, of course. This changes in season seven, when the Leviathan soon learn how well they can use society's infrastructure against the Winchesters, and the Impala is hidden for most of the season, and the brothers rely on stolen cars for half the time.
In "The French Mistake", this continues with Sam and Dean transported into the bodies of their actors Jared and Jensen. This despite the fact that both actors are married—wait a minute.
Monochrome Casting: The vast majority of the cast is white, though there are some background characters of varying ethnicity. Almost all recurring characters are white, the few exceptions tend to die horribly (but then again, who doesn't?).
Monster Lord: Azazel, Crowley and Lilith are powerful, high-ranking demons. Bobby refers to Death as the "Big Daddy Reaper". The Alphas and Mother of All also count.
In "Mystery Spot", Dean keeps dying, we laugh hysterically because they're showing the funny ones, and then Dean dies for real, which breaks Sam completely, and we feel guilty for ever laughing at all.
Notable in "Swan Song."
Castiel: He'll be back, and upset, but you got your five minutes.
Lucifer: Castiel...did you just Molotov my brother with holy fire?
The sixth season episode "Live Free or Twi-Hard" starts with a dead-on Twilight parody but switches to angsty after the first act.
Ghostfacers has a lot as well. Between the incompetence of the Ghostfacers crew, the depressing ghost's story, Corbitt's death and Ed's tearjerker farewell and the Ghostfacers bumps before every commercial break, the episode is all over the mood map.
Moral Dissonance: The Winchesters seem to care less and less about killing the demons' human hosts as the show goes on, though this may be a result of the sheer number of demons they encounter. And Dean's Moral Myopia means he'd rather kill them all than risk Sam using his powers to save the hosts, especially once he finds out demon blood fuels them.
Moral Myopia: Dean's attitude towards the possibility of Sam turning into a monster or otherwise being abnormal; he's perfectly willing to kill strangers who might go darkside, but simply refuses to do so with his brother even when presented with clear indications of this happening, because he couldn't bear to live without him.
The Multiverse: As of season 6 we have Earth, Heaven, Hell, Purgatory, an alternate future, the Trickster's alternate realities, the universe where their lives are a TV show, and of course, Fairy World (of which ''Oz'' is a subset, as of S9). The Masquerade for normal humans has gone beyond just covering up for things that go bump in the night (oh, and the apocalypse). And, of course, Heaven itself is a mess of alternate realities strung together.
Mundane Afterline: Once Crowley takes over hell, he dispenses with the lava, thunderstorms and chains and makes everyone wait in line for eternity. When they get to the front, they go right back to the end again. "That's efficiency." Oh, and for some reason they're all dressed like Sam and Dean.
Mundanger: The series has featured a couple of these: a Cannibal Clan in "The Benders" (named after a real-life cannibal family nicknamed The Bloody Benders) and feral children in "Family Remains".
Mundane Solution: Decapitation is only a minor setback to a Leviathan, but they can be burned by Borax, which can be found in common household cleaners. They regenerate even from that, of course.
Murderous Mannequin: In "Mannequin 3: The Reckoning", the Monster of the Week possesses mannequins to kill its victims. It sure was lucky that all of its targets happened to work with mannequins or use sex dolls, though.
Must Make Amends: Season five is this for Sam after accidentally starting the Apocalypse and freeing Lucifer and in response to his behavior in season four. The second half of season six starts like this for him after he finds out what he did while soulless.
Must Not Die a Virgin: Just before an encounter with an archangel that the characters believe will prove fatal, Dean, on hearing that Castiel "never had occasion" to lose his virginity, attempts to set him up with a hooker (called Chastity, no less). Hilarity Ensues.
Neck Lift: The demons are fond of this. Notably, Azazel to Dean in a drug-induced vision and Alastair lifting up Dean and placing him on his own torture rack while berating Dean on the sloppy job he did on Alastair.
Neck Snap: Most bad guys prefer this method of killing someone, with demons usually doing it with Telekinesis. Since it's mostly supernatural beings, the ease with which the neck breaks is justified. Most notably, this is how Lucifer eventually kills Dean in an alternate future.
Necromantic: Shows up in a season 2 episode by way of an ancient Greek resurrection spell.
Never My Fault: Lucifer sees himself as a Woobie, Destroyer of Worlds, and for the longest time in the show you believe him. He's constantly saying how wrong it is that he was a faithful servant of his father, and his only crime was to not bow down before humans, and with how imperfect they are, you can hardly blame him. Then in "Hammer of the Gods", his younger brother Gabriel reveals the truth: he wasn't forced to bow down before them, it was the fact that God loved him most of all before transferring his affections to humans. In retaliation, Lucifer twisted a human soul into a demon, trying to get his father to admit they were horrible creations and destroy them, thus getting to be front and center again. Death even refers to him as a bratty child having a temper-tantrum. He gets called out on it again in the season 5 finale, when Lucifer is about to have his climatic showdown with his older brother Michael. He tries to talk Michael out of it by saying that God controls everything, and thus he forced Lucifer to be the devil, so it's not his fault. Michael promptly says that he hasn't changed a bit and he's still blaming everyone but himself for what he did.
New Era Speech: Castiel gives one to what remains of the Host of Heaven after he's done killing most of them.
Castiel: Understand... if you followed Raphael, if you stood against me... punishment is certain. There is nowhere to hide. The rest of you - our Father left a long time ago. That was hard. I thought the answer was free will. But I understand now - you need a firm hand, you need a Father. And I am your Father now. Be obedient, children... or this will be your fate. [motions to hundreds of angel corpses on the ground] It is a new day... on Earth and in Heaven. Rejoice.
At the end of season four, Sam spends most of the season getting the power to kill Lilith so he can stop her from breaking the final seal and freeing Lucifer. In actuality, Lilith was the final seal, and by killing her he causes the release of Lucifer and kick-starts the Apocalypse. Oops.
At the end of Season six, Castiel absorbs the monster souls of Purgatory to get the power to defeat Archangel Raphael, who wanted to restart the Apocalypse. But in doing so, he unleashes the Leviathans, creatures that God locked away to stop them from eating everything else.
To an extent, Dean as well, not only for breaking the first seal between seasons three and four, but also for revealing to Azazel beforehand that his plans were going to work.
Sam and Dean are unable to kill Abaddon so instead they dismember her and bury the pieces. Later when they find out about the final trial to shut hell they decide to use her as a test subject. She gets loose while they're on the phone with Crowley
By finding Metatron and bringing him up to date on recent events (such as the failed apocalypse and that the Arch Angels are dead or sealed up) set into motion his plot for revenge, using Castiel as his Unwitting Pawn
Zachariah sends Dean into a bleak future to convince him he must say yes to Michael. The trip also convinces Dean he has to stick with his brother, which lets Sam talk Dean out of the Michael thing and lets Dean give Sam the strength to take control of his body from Lucifer long enough to throw him back into the Cage.
Famine reawakens Sam's craving for Demon Blood and sends two of his men to be "snack" for him, knowing that unlike everyone else affected Sam can't die from having too much, and makes him powerful enough to kill demons. When Sam simply exorcises Famine's demonic bodyguards, Famine chooses to devour them. while Sam's powers don't work on Horsemen, he can painfully kill the demons inside of Famine.
Could be construed as the case with Naomi's handling of Castiel. Cas was able to easily beat Dean badly enough that he would not have been able to prevent Cas from simply taking the tablet and teleporting away. Indeed, he could have overpowered Dean and taken it as soon as Dean had it out of the box. But Naomi's insistence that Cas kill Dean led to him breaking free of her control. A classic case of a villain overplaying their hand.
God: Pagan gods can be killed by mere mortals, but the trope does apply to the Big G, since it seems like Death is the only entity that could kill him.
Divine protection mixed with Resurrection: In season 5 Sam and Dean are functionally incapable of staying dead. If they do die then the angels (in Sam's case, specifically Satan) will just resurrect them because they can't be used as angelic vessels if they're dead.
External Repair: Dr. Benton is a scientist who somehow gained immortality, but his body kept on decaying. In order to continue functioning he regularly harvests new organs.
Regeneration: The Leviathans recover from almost anything. The only known means of immobilizing them so far is to chop off the head, and then keeping it absolutely out of reach of the body so it can't just reattach itself. The only thing that can kill a leviathan is the bone of a righteous person dipped in the blood of the king of hell, an alpha monster, and a fallen angel. These ingredients are nigh impossible to obtain.
In "Criss Angel Is a Douche Bag," Criss Angel never shows up, but the show makes fun of him through a character named Jeb Dexter, an incredibly arrogant magician who bears an incredible resemblance to Criss Angel and does card tricks that are staged like fake demon possessions (which really upsets Dean). He dies horribly, of course. The show also makes fun of him, quietly, by naming the episode Criss Angel Is A Douche Bag
Castiel delivered one of these to Dean Winchester, when Castiel caught him attempting to surrender to Michael, which the angel considered a betrayal.
In 4x16, when Alastair unexpectedly freed himself from the devils-trap. And having been tortured by Dean for a few hours, he was quite pissed.
In the season 5 finale, Dean puts himself on the receiving end of such a beatdown when he refuses to leave his brother while Lucifer is possessing Sam.
In 6x13, a soulless-Sam gives one to a cop who's grown suspicious of his cover.
In 8x17, Cas, under Naomi's control, gives a serious one to Dean. Fortunately, Cas breaks free of Naomi's control before killing Dean, and heals the injuries he inflicted.
Nostalgia Heaven: Except that, because you become distracted by the projections of your friends/family, instead of actually getting to meet up with your loved ones, the characters who find out are decidedly unhappy.
Dean: …the truck stop waitress with the bizarre rash…
From "And Then There Were None", and possibly "When the Levee Breaks", there's the situation in Omaha between Bobby and Rufus.
Sam: Martin is a great hunter.
Dean: Was... until Albuquerque.
In "Out With The Old" Sam and Dean are tracking down a cache of cursed objects an antique store has unknowingly unearthed and sold off piece by piece. The objects compel people to kill themselves in a Turned Against Their Masters sort of way (with a dash of Death by Irony). (For example, an antique tea kettle compels a woman to kill herself by pouring the boiling water down her own throat). Sam and Dean split up to get the last two, Sam going after a gramophone an Dean going after an antique "gentlemen's magazine".
Dean: How does porn kill a guy?
Sam: You probably don't want to know.
Dean: Hey, got the porn. Just in time, too.
Sam: What was he doing?
Dean: Uh, like you said; you don't wanna know.
No Sell: This happens quite often. To name but a few:
Earlier in the series, Dean gets into an argument with the angel Castiel that ends with Dean punching him in the face. Cas' head moves a little from the impact, and Dean nearly breaks his hand. And he clearly didn't learn his lesson, as he does the same thing in a later episode with a Cupid, with the exact same result.
In "Hammer of the Gods", Lucifer gets immolated completely by the Hindu goddess Kali, but when the flames dissipate he's still standing in the same spot looking almost bored.
Lucifer gets another good one after being shot by the Colt. After a moment when it looks like it's all over he gets up and spits out the bullet.
A particularly amusing example was Sam's nonchalant immunity to Veritas' truth-inducing powers, and the epic fit she throws when she realizes he can lie to her with impunity.
Used rather terrifyingly with the Leviathans. For the first quarter of the season the only thing that worked was dropping a car on Edgar to slow him down or cutting of their heads and separating them from their bodies. The only way to kill them is with a bone of a saint dipped in the blood of and Alpha monster, a fallen Angel and the king of Hell.
Michael and Lucifer lecture Dean and Sam about this, who are their respective vessels. Michael tell Dean that he is dutifully obedient to his father (God), that he cast Lucifer down because he defied him, and that he practically raised his younger brother, taking care of him "in a way most people could never understand". Lucifer tells Sam that he loved and idolized his older brother and begged him to stand alongside him in refusing to bow down to humanity, but that Michael instead called him a "freak" and a "monster", casting him down because he was different and had a mind of his own.
Eve gives this speech about herself and their mother in "Mommy Dearest".
Off the Rails: The angels. All of them. It seemingly started with Lucifer, but has only been getting worse over the ages as God has continued to refuse to speak to any of them except for Joshua (allegedly). At present even devout angels who long resisted succumbing to despair over God's absence, such as Castiel, have all broken ranks to pursue their own agendas. God, if He is in fact Chuck, appears to be finding this entertaining and is allowing everyone to do whatever they choose while making quiet adjustments from behind the scenes now and then to keep the game running, such as ensuring that none of the main characters stays dead for long.
Offing The Annoyance: During Death's character-defining intro in "Two Minutes To Midnight", he takes a stroll in Chicago looking like a normal human and a rude guy too busy with his phone makes the mistake of bumping into him and scolding him. Grim barely glances back, slightly brushes his coat as if getting rid of a pesky fly, and the guy immediately drops dead right on the street. As is later seen, it's not used to villainize him however; he just operates on such a larger scale that he actually is just getting rid of what to him is nothing more than a petty microbe.
Primary mode of travel for angels. Though it's sometimes only offscreen for the audience; there've been a number of instances of Sam or Dean watching as an angel vanishes.
Crowley can do this, and quite possibly is better at it than Cas. When Cas does it, you hear wings. When Crowley does it, you hear nothing. Considering that Crowley is a demon, this is quite possibly intentional Paranoia Fuelinvoked on his part. It's also a sign of upgraded-Cas' power that he can do it silently now.
It also seems that any demon that is summoned will also teleport, and it will also do it offscreen.
In Season 6, Eve, like the angels, is capable of doing this while Dean is looking directly at her. She just appears behind him, and still somehow manages to surprise him.
Combined with a huge Take That at fans who write things like that in the form of Becky, who admits to Chuck and Sam that she writes a lot of the stuff out there and is designed to be The Scrappy.
Dean: They do know that we're brothers, right?
Sam: Doesn't seem to matter.
Older Than They Look: Sam and Dean have both aged mentally several decades beyond their physical ages. Dean spent around 40 years in Hell, which means that he's mentally in his early 60s. Sam spent over a hundred years in Lucifer's Cage (it's not explicitly stated how long though). This is not touched on much in the series.
This may have something to do with the mind and the soul being separate. Dean experienced 40 years of torture, but, being a disembodied soul at the time, he didn't age mentally as you would expect of someone living out their life. This, however, is not explored in the show or addressed by the creators, so it's largely a matter of interpretation.
Likewise Sam comes back without a soul and when this is fixed there is a wall put up to protect him. After it is torn down by Cas he becomes insane but Castiel absorbs all of his insanity
Death is functionally omniscient. Every time Dean tries to tell him something, the bored-looking Grim Reaper notes that he's already aware. He does show surprise when the Winchesters summon him and ask him to kill an evil god for them, so it seems he needs to focus his all-knowing powers for it to be effective.
God, naturally, also seems to possess this trait. When they try to ask for his help, he relays through an Angelic messenger that he already knows everything they want to tell him, he just doesn't care. He did write their story, after all...
One Bad Mother: The Mother of All is the progenitor of all monster races, and resides in Purgatory, the afterlife where all monster souls go to prey on each for eternity. She eventually returns to Earth to protect her young by making everyone on the planet one of her children. To make the point even more obvious to Sam and Dean, she transforms into their deceased mother Mary Winchester to mess with them.
Only the Chosen May Wield: Dean has to pull a sword from a stone in "Like a Virgin". When it doesn't work, he just blows it up.
Ooh, Me Accent's Slipping: Inverted; Sam seems to become more and more Southern as the series goes on. While his actor is a Texan, Sam's earlier accent is closer to Jared's. While Jensen Ackles is also a Texan, his accent is nothing like Dean's. Dean's accent has also gotten more Southern, though a lot more overtly.
Other Me Annoys Me: In "The End", both Mes are annoyed (or, you know, scared by) their Other; in "The French Mistake", Other Me manages to be annoying without actually being present
Our Angels Are Different: As Dean puts it, they're more "dicks with wings" than Roma Downey. Like demons, they posses (albeit willing) people in order to move about on Earth, and they can relinquish their grace and be reborn as humans.
Our Demons Are Different: The souls of the damned who've had their humanity tortured out of them in Hell, they appear as black smoke unless they are possessing someone.
Our Dragons Are Different: ancient beings from purgatory who resemble "Giant Bats", have heat-hands, can shapeshift into human form and serve a being they only refer to as "Mother" and can only be killed by a weapon forged in their blood. They also have hoards of gold and collect virgins for their rituals.
Our Genies Are Different: In "What Is and What Should Never Be", the Winchester brothers track down a djinn that appears to grant whatever its victim wishes for, altering the world around them. But Dean learns first hand that the djinn just puts his victims in an acid-trip-like state, hooks them up to an IV, and drinks their blood for a few days until they die (but it feels like years in the djinn-induced-acid-trip). The victims do occasionally get flashes of reality, though, which allows Dean to figure out what's happening and escape.
Our Ghouls Are Creepier: Ghouls are of the Arabian demon variety and take the appearance of the last person they have fed upon. Though to give an actual reason for why they have to be killed (saying that they desecrate human remains would be a bit weak when the Winchesters have to have burned a whole cemetery by this point) the ones they encounter have started eating living people. Funnily enough the second set of ghouls they encounter are also perfectly happy to eat the living. What, did a ghoul write an awesome new recipe book for fresh meat in the last few years?
Our Gods Are Greater: The series seems to be based on Henotheism - there are multiple pagan gods (who are scarily powerful but can still be defeated and killed), with the Judeo-Christian Creator God as the one that is actually omnipotent but inaccessible. Appropriately enough "Word of God" confirms American Gods was a major influence on Supernatural, so it likely works on similer rules. Therefore, Kali and Ganesh were simply versions of the gods brought over by settlers. In America, a largely Christian country, an Judeo-Christian angel is more powerful. Had the fight taken place in India, it would have been a different result.
Our Souls Are Different: You can sell 'em to demons (or angels!), string 'em up in Hell, and torture them! And when you need to move 'em around, a briefcase is all you'll need (admittedly, this was the means of soul transportation employed by Horsemen of the Apocalypse, not that of a mortal human). Humans can apparently survive without them, and simply lack emotions, empathy, and the need to sleep when lacking one. Monsters have them too, while ghosts and demons are respectively trapped and corrupted souls. Angels don't have them. Nor do Leviathans, being far older than the creation of souls.
Our Titans Are Different: Chronos shows up in season seven as a time traveler who needs to kill to control where he can time travel to, and is seeking to get back to his love. An amnesiac Prometheus shows up in season eight.
Our Vampires Are Different: They are. This is lampshaded in Monster Movie, where they encounter an apparently typical Bram Stoker Dracula and are completely baffled. The really funny part is that the witnesses immediately identify it as a vampire, whereas this would probably not be the case with an actual vampire.
It might have been a better plan if John told his son Dean what's going on and ordered him not to come after him instead of just taking off, leaving Dean to think he did something wrong or that something bad happened to John.
God vanished, leaving the soldierly angels without a father or direct orders.
Played with in the case of the Winchesters. Throughout Season One, Sam thinks that John hates him (when he left for college, he told him to never come back) while Dean is the one who obsessively follows his Dad's orders and can't seem to comprehend not following an order. But it's slowly revealed that Sam is the one who John cares the most about (although this could just be through the eyes of Dean) while Dean is the one who had to grow up too fast and was treated, well, more like a soldier than a son. Although John did try to make it up by doing a deal to save Dean's life, Dean's Daddy Issues (the fact that he still thinks he wasn't good enough for him and that he still thinks he's the one who should have died) continue to this very day. And the Yellow-Eyed Demon knows this. He even taunts Dean by saying that John arguing with Sam was 'more concern than he's ever shown you.'
Also exists among the angels, as Gabriel points out that they all know that "He loved you best. More than Michael, more than me", discrediting Lucifer's claim that he hates humans because God loved them more. Gabriel reveals that Lucifer hates humans because he thought that God preferred them over him.
Parents as People: Whether you think he's a useless bastard of a so-called father or a good guy just trying to raise two pretty difficult kids (if "Tall Tales" and "Hell House" were anything to go by) on his own under horrible circumstances, you have to admit that John is just as multi-layered and complex as Sam and Dean.
Parody Episode: Supernatural likes to play with this trope once a season (in its second half)—while the Winchester brothers are still chasing a mystery, the format and/or subject matter of the episode (and their case) takes a comedic tone and it becomes obvious that it's parodying something:
While trying to hack into Frank's encrypted hard drive, Charlie thinks she found the password in the remarkably simple "WarGames" when this yields results. Then Frank's hard drive opens a program revealing that it's a false lead and taunts her.
Played straight while she's hacking into Dick Roman personal computer, which is locked by the password "W1nn1ng".
People Farms: It is ultimately revealed that this is the plan that the Leviathans were working on all through Season 7 — they create a food additive drug that, upon ingestion, makes humans slothful and complacent, causing them to fatten up and dull up, so that they can be marched into the slaughterhouses the Leviathans are building under the guise of agricultural factories. Oh, and the drug is lethal to any other monsters that feed on humans, since the Leviathans don't want any competition for their food.
Person of Mass Destruction: Castiel briefly becomes one at the end of season 6. While he was already quite a powerful supernatural being to start with, he upgraded himself with what essentially amounts to a supernatural nuclear reactor: 40,000,000 souls from a transdimensional monster afterlife. He goes mad with power and goes around killing hundreds if not thousands of people around the globe and showing his godly 'benevolence' by performing miracles. It's repeatedly mentioned that he's unstable and might take a large part of the planet with him when he reaches critical point. He's eventually compelled to give up his powers because he's housing far meaner beasties inside him.
Phone Call From The Dead: In the episode "Long Distance Call" several people, including Dean, seem to get this kind of call from deceased loved ones.
Phony Psychic: Sam and Dean run into an entire town of these in "The Mentalists". Lampshaded to no end, but particularly when Dean mentions that Pamela was one of the few genuine psychics they have encountered. There are actually some real ones as well, including the villain, who has summoned the ghost of a dead psychic to kill the impostors, while her equally psychic and ghostly sister tries to warn people about her.
The various Pagan and other non-Abrahamic gods seen in the series are all physical beings with tremendous powers, but can be killed with the right weapons.
The Trickster. Here, a Trickster is a pagan god. He can reshape reality and mess with time. Dropped a guy into a wormhole For the Evulz. Good times. A few other Pagan gods have also featured in the series. In season 5 it's revealed that the Trickster is actually not a pagan god at all, but an Archangel, specifically Gabriel, who's hiding from his brothers.
The demons revere Lucifer as a god because he created their race. After he gets released, Meg directly describes the archangel in these terms to Castiel.
Meg: Lucifer is the Father of our race. Our Creator. Your God may be a deadbeat, but mine... mine walks the Earth.
At the end of season 6, Castiel becomes one. Or at least that's what he claims. He proceeds to take a very active role in managing his new kingdom, roasting half of Heaven, killing people all over the world who displease him, and presenting himself as a wrathful but just deity.
Poor Communication Kills: Half the time, lives could have been saved if the brothers just came out and said they were paranormal investigators from the start, without trying to pass themselves off as cops.
In "The Monster at the End of This Book," the Winchesters discover they are the lead characters in a series of horror novels with a small but fervent fandom. Online research turns up fan criticism, Samgirls, Deangirls...and slash fiction. When the boys track down the author (who at first believes they are his fictional characters brought to life), he apologizes for all the emotional torment and bad writing they've been subjected to.
invokedWhen they meet a fangirl who writes Sam/Dean slash fics...well, you can imagine. The boys are understandably squicked.
Dean: They do realize we're brothers, right?
There's an episode where they end up at a Supernatural convention.
The episode where Sam and Dean end up in an alternate dimension where their life is a TV show called "Supernatural". They have to act. It isn't pretty.
Power Trio: Sam, Dean, and Castiel (circa Season 5). They even have the in-canon team name "Team Free Will".
Dean: An ex-demon-blood junkie, a high school dropout with six bucks in his pocket, and Mr. Comatose over there. Awesome.
Pragmatic Villainy: Every time a Deal with the Devil is made, the victim is supposed to get to live for 10 more years before the demons come for him. Crowley is outraged when a lesser demon comes for his victims early:
Done in "Heaven and Hell", except a girl (actually, an angel who has lost her "grace") suggests that to Dean, who is a little put off by the fact that it's usually him who tries to do the same. It doesn't stop him, though.
Subverted in "Abandon All Hope..", where Dean tries to do it with Jo, only for Jo to say that if this is really her last night on this Earth, she'll spend it with dignity.
The monster hunters dislike wannabe-hunters, since they tend to derive their knowledge of monsters from popular fiction - which can get them and others killed. When Dean meets Samuel, Samuel tests him with a question about vampires that a wannabe would fail.
Sam and Dean are also very derisive of Vampire Wannabes and vampire fandom in general. Supernatural's vampires are, with very few exceptions, brutal killers who will use their fans for food without second thought. And the exceptions don't act anything like Pattinson.
Death himself delivers one to a power-tripping Castiel in the season seven premiere. "I know God, and you, sir, are no God."
The Problem with Fighting Death: Discussed. To stop Lucifer, Dean tries to kill Death, unaware that he could've gotten what he wanted without killing him, as they both had a common interest in stopping the "bratty child". Dean assumes that Death would be angry at this, but it turns out the problem with a human fighting Death is that the human just doesn't matter.
He later gambles with him and buys him a hotdog, but continues to impress upon him the depths of his insignificance at every opportunity. It's here that Death also clarifies that he himself cannot, in fact, die.
Proscenium Reveal: "Hollywood Babylon" opens with two terrified 20-somethings, Wendy and Brody, in the woods. Brody runs away; Wendy calls for her friends, hears a noise, turns toward the camera and screams — unconvincingly, at a tennis ball stuck on top of a movie camera. "Cut!" calls the director. "Wendy" is actually Tara Benchley, the lead actress of Hell Hazers 2.
Psychic Dreams for Everyone: Averted averted averted. Sam's psychic powers begin as harmless visions that help them save people in peril, but still cause all main characters to completely freak out because they must be evil. Turns out, they are.
Psychic Nosebleed: Sam, when he uses his psychic exorcism powers against particularly difficult demons.
Psychic Powers: Sam and the Special Children. Pamela Barnes and Missouri Mosely are more garden variety clairvoyants.
Psycho Serum: Sam Winchester spent half the season break between three and four, and all of season four, using demon blood to enhance psychic powers conferred upon him by feeding him demon blood as a baby. This allows him to kill demons without necessarily killing their hosts, a power no one else in the setting except angels ever demonstrates, and angels rarely bother. There turn out to be three definite problems with the system:
The woman providing him with it is engaged in a long-term manipulation to help the current Big Bad with her Thanatos Gambit to free Lucifer.
Most definitely an unavoidable problem: The stuff is incredibly addictive, and his growing addict behaviors are not good for any other part of his emotional life.
It apparently is, to some degree, slowly turning him into something other than human. To what degree his bad behavior stems from this instead of straightforward addiction is impossible to determine; he never seems to approach outright Transhuman Treachery, and he demonstrated a capacity for being dangerously obsessive before he started on the stuff. A majority of his choices were actually pragmatic logic for the greater good, but they sure wrecked his relationship with his brother, who has this weird power to be right about everything even when it's for the wrong reasons.
Pulling Themselves Together: The Leviathans have a regular Healing Factor, but when their heads get cut off, it instead reattaches itself to the body if left alone for too long. The Winchesters and Bobby use this to figure out a semi-permanent way of dispatching them by storing the body parts far away from each other.
Puppy-Dog Eyes: Mostly Sam and Castiel, although Dean can also manage to look like a stomped-on puppy at times.
The end of season five: Sam and Dean manage to defeat Lucifer, but at the cost of Sam having to jump into Lucifer's cage. Particularly heartbreaking because all Dean was trying to do was save his brother for most of the series. \