- in 1x05, Dean’s eyes bleed when he confronted Bloody Mary, which only happens to people who feel responsible for a violent death. Kripke said there was a reason why Dean’s eyes bled and it was a “dark secret”
- prostitution and/or sexual abuse; Dean recognises the smell of chloroform in 2x06, is always uncomfortable being referred to as ‘pretty’, and when Jensen was directly asked about sex work in Dean’s youth, he said: “it’s definitely implied that there are poker games and pool matches that they can win some money on. and who knows? Dean’s a promiscuous kind of guy. who knows how he drums up the funds that they use?”
- Dean’s jewellery; we know why he stopped wearing the Samulet, but in early seasons Dean also wore a silver ring, and sometimes bracelets with protective symbols on them. where did they all go?
- the Righteous Man; this huge mytharc was utterly annihilated by the writers in the close of S5. Dean bears a mysterious handprint from Cas and in 4x16, Cas explains that the Righteous Man who sheds blood in hell is the only one who can end the Apocalypse…
- Dean’s immunity to Famine and War. especially Famine - why was his emptiness any different than the emptiness that Sam, Jimmy, the lovers who ate each other etc, felt?!
- Dean is able to kill the Whore of Babylon in 5x17 because he is a “true servant of Heaven”, even though Cas said he wouldn’t be eligible for that title
- in 5x18 Dean watches Zachariah die and doesn’t suffer for it. angel light blinds normal humans - and only angels are supposed to be able to kill another angel. instead of burning, Dean’s eyes glow opalescent when he destroys Zachariah, and he is also unaffected when Michael’s unvesseled light begins to fill the room - while Sam turns away from it, and at the start of the episode two civilians are completely annihilated by it.
- Dean is the Michael Sword. archangels have one true vessel. if they exert too much power in the wrong vessel, the human they’re wearing starts falling apart, as shown by Lucifer wearing Nick in S5. but somehow, Michael is content to use Adam and John as replacements for Dean- he is burnt alive by holy fire while wearing Adam, yet manages to knit himself back together in a matter of minutes in 5x22, with his vessel showing no ill effects
- in 6x05 vampire!Dean gets visions from the Alpha which are never explained, and for some reason he is unaffected by Eve’s call to war
- Dean gains the ability to see faeries on Earth in 6x09. we never learn what the faeries wanted with first born sons, or why in 8x11, everybody can see Gilda the good fairy and not just Dean
- when Dean loses his bet with Death in 6x11, Death agrees to fetch Sam’s soul in exchange for Dean investigating souls. for some reason, Dean never follows through with this, and is rightly chastised for it in 7x01
- in 6x18, Dean kills a Phoenix with the Colt, and drinks its ashes in 6x19; for some reason this doesn’t effect him in any way, when a human imbibing the essence of a creature in SPN almost always results in turning into that creature
- in 7x13, when Dean has sex with Lydia, we see that the handprint Cas branded him with in 4x01 has magically disappeared (it was later revealed that the writers actually forgot it was supposed to be there)
- in S8, Dean almost single-handedly tears Purgatory apart to find Cas, and is devastated about leaving him behind. when Cas is revealed to be alive, the season progresses with romantic subtext, while Dean and Cas attempt to work through their issues, culminating in an explosive confrontation 8x17. Dean is able to break Naomi’s hold over Cas by saying “We’re family… I need you” - a line that was originally supposed to be I love you, but was changed because Jensen refused to say it. throughout the rest of S8 and all of S9, Dean and Cas never take a moment to acknowledge that they’re in love with each other
Dude this list is everything
(they also forgot the handprint in 6x01 and explained it away by saying that in 5x22 when Castiel heals Dean he removes the mark)