|“||I will never lie to you, I will never trick you, but you will say yes to me.||”|
"Yes", as attributed to assenting to an angelic being, is the way an angel is allowed to possess a human vessel. It was a critical issue for Sam and Dean Winchester during Season 5, who were the predestined vessels of Lucifer and Michael respectively during the Apocalypse. As seen in Ouroboros, a "yes" doesn't have to be verbal and can instead be a simple nod of consent.
Also, as can be attested in Swap Meat, the permission need not necessarialy be from the person who actually owns the body, but from any human soul who happen to be currently possessing it after a body-swapping spell. This means that angels could possess any uncooperative host if they somehow managed to swap their vessel's soul with a more weak-willed or gullible individual's.
- The Rapture - Castiel converses telepathically with Jimmy Novak to get him to become his vessel and he eventually says Yes in exchange for the angels protecting his family. Later, his daughter Claire apparently says Yes to Castiel, presumably to save her family, as he is able to briefly and safely possess her as she is Jimmy's daughter. While Jimmy doesn't outright say Yes again to Castiel, his insistence that Castiel takes him as a vessel again to spare his daughter is apparently enough.
- Sympathy for the Devil - Talked about by Zachariah, who tells Dean of his destiny as Michael's vessel and tells him to say Yes to Michael so the latter could defeat Lucifer. Dean says the answer is No. Zachariah tries to torture him and Sam into compliance, but Dean refuses to break and Zachariah is forced to flee when a newly resurrected Castiel shows up. Lucifer appears to Nick, who eventually consents to possession.
- Free To Be You and Me - Lucifer reveals Sam is his vessel while asking Sam to say Yes, though Sam says No. Lucifer assures him that eventually he will say Yes but promises that he won't force or deceive him to do it.
- The End - In an alternate timeline, in 2014, Sam assents to Lucifer in Detroit; Future Dean implored his counterpart to consent once he goes home but knows he won't and the future counterpart said if do it over again, he would say 'Yes' to Michael in a "heartbeat". Zachariah again tries to convince Dean to say Yes to Michael, and again Dean refuses. Dean is rescued by Castiel after Zachariah promises to torture him.
- Changing Channels - Gabriel captures and commands the Winchesters to say Yes; they both refuse and trap Gabriel.
- Abandon All Hope...- After Dean fails to kill Lucifer with The Colt, Lucifer tells Sam that even if Sam won't consent now that he has foreseen Sam saying Yes and that it will happen within six months in Detroit.
- The Song Remains the Same - Michael himself speaks with Dean and insists that it is his destiny to say Yes after having gotten John Winchester to say Yes by promising to save his wife.
- Dark Side of the Moon - Zachariah is angry with Sam and Dean for their continued refusal; since they were dead he planned to beat them up regardless of whether or not they say Yes. He was stopped by Joshua.
- 99 Problems - Sam starts to worry that Dean will say Yes to Michael.
- Point of No Return - Dean almost says Yes to Michael, but Castiel, Sam, and Bobby stop him. Under coercion from Zachariah, Dean finally says Yes to Michael, but changes his mind, kills Zachariah and escapes with Sam, though Adam is left behind and is later revealed to have been taken by Michael as his alternate Winchester vessel, having earlier agreed.
- Two Minutes to Midnight - Sam decides to say Yes to Lucifer as part of the plan to re-imprison him in the Cage.
- Swan Song - Sam says Yes to Lucifer. Lucifer, despite knowing Sam's true intentions, possesses him.
- I Think I'm Gonna Like It Here - Hael planned to possess the then-graceless and effectively human Castiel in order to become stronger and tried to threaten him into saying Yes after being badly injured, but Castiel killed her instead. In order to save Sam, "Ezekiel" takes on Dean's form and converses with Sam in his mind, convincing him to say Yes to "Dean's" plan to save him which proves to be enough to allow "Ezekiel" to possess him and heal him from within.
- I'm No Angel - Bartholomew is using an internet preacher to get devout people to say Yes when angels come asking them to be their vessels. A young woman comes to Bartholomew and offers herself up, but proves to be an unsuitable vessel and explodes.
- Heaven Can't Wait - A young man says Yes to Ephraim who proceeds to go on a rampage, killing everyone he can find who feels any sort of emotional pain before being stopped by Dean and Castiel.
- Holy Terror - Bartholomew has started having the preacher, Buddy Boyle, target smaller groups for possession in order to ensure his own followers get vessels and not everyone else. Malachi and his faction do the same using a choir woman possessed by one of his followers to target a group of college students, but the students are killed by angels working for Bartholomew before they can be possessed.
- Road Trip - Sam revokes his permission to Gadreel, expelling the angel who is forced to return to his original vessel who once more says Yes.
- Mother's Little Helper - Josie Sands tried to give her permission to the Knight of Hell Abaddon, but she laughed and said that the demons didn't need it.
- The Devil in the Details - Lucifer tries to get Sam to say Yes again by taking him through his memories, then resorting to violence when Sam still refused. After Dean and Castiel arrived to stall Lucifer until Rowena can banish him, Lucifer possesses Castiel after he consents, nullifying Rowena's spell and escaping the cage again.
- Mamma Mia - Lucifer gets Vince Vincente to say Yes by taking the form of his deceased lover.
- LOTUS - Lucifer, in a bid to increase his influence over the world, telepathically speaks to US President Jefferson Rooney, promising to make America a Christian nation once again if Jefferson would say Yes, to which he agrees.
- Let the Good Times Roll - After Lucifer becomes supercharged by stealing Jack's grace and kidnaps Jack and Sam, Dean offers the Apocalypse World Michael a deal where he will say Yes to Michael to fight Lucifer if Michael allows Dean to remain in control while Michael powers him. Michael agrees to the deal and Dean says Yes, enabling him to kill Lucifer. After Lucifer's death, Michael reneges on their deal, takes full control of Dean and departs.
- The Spear - The Apocalypse World Michael is able to retake possession of Dean without Dean saying Yes again as Michael left the door open a crack in Dean's mind when he left so that Michael could return at will.
- Ouroboros - After escaping Dean's mind, the Apocalypse World Michael leaves his body and approaches Rowena MacLeod to act as his vessel. Michael threatens to return in another vessel and slaughter everyone in the Men of Letters bunker if Rowena says no, but promises to spare everyone if she says yes. With a simple nod, Rowena reluctantly grants her consent, allowing Michael to possess her.
- Proverbs 17:3 - Sam sees God's memories of an alternate reality where his alternate self said Yes to Lucifer and remains possessed.
- Our Father, Who Aren't in Heaven - Adam Milligan, still the vessel of the archangel Michael, reminds Michael that Sam and Dean tried to stop Adam from saying Yes to Michael as proof that they always try to be on the right side.
- In the non-canon book Supernatural: The Men of Letters Bestiary: Winchester Family Edition, it is stated that all Special Children are suitable vessels for Lucifer.