Sam and Eileen may have finally gotten their moment (sort of) in the latest episode of season fifteen, but Supernatural has still left loads of unfulfilled romantic potential between its characters. Over the years, the characters of the show have gone through countless life-threatening situations, and the lives they live don't always make it easy to start passionate love affairs.
Although Supernatural is, by no means, a romance, the characters it has introduced develop relationships that add complexity to the stories told episode by episode. But some of these relationships are cut short or abandoned altogether, leaving fans feeling unsatisfied.
Charlie & Dorothy
When Charlie visits the Bunker in the season nine episode "Slumber Party," she uncovers Dorothy Baum, daughter of Frank L. Baum, Man of Letters and author of The Wizard of Oz. The two exchange flirtatious banter throughout the episode, and by the end, Dorothy invites her to join the rebellion in Oz, to which Charlie agrees excitedly.
While Dorothy has never stated a preference, Charlie has always been open about her sexuality, so it's easy enough to assume the two had at least a conversation about a relationship. Charlie returns to Earth a year later, without Dorothy and without any indication that anything happened between them. Even if Dorothy were to return in future episodes, Charlie was killed in season ten, so the pair would still be left a loose end.
Bobby & Ellen
The main world versions of these two characters only shared the screen briefly in a single episode, the same episode in which Ellen and her daughter Jo are killed, but a universe where the Titanic never sank, and the Winchesters drive a Mustang, also features Bobby and Ellen as a married couple.
The pairing almost seems random at first glance, but a closer look reveals just how much they have in common. Both are seasoned hunters who were widowed at the hands of demons. At the point when the episode "My Heart Will Go On" takes place, they are each other's only love interests, aside from their late spouses. Considering all this, it's a mystery why their relationship hadn't been explored while they were both alive.
Anna & Castiel
When Anna is introduced in season four, angels are considered emotionless beings, free of the desires of humankind, though a handful of relationships have formed between angels since then. Anna even has a brief fling with Dean before getting her grace back. Before she fell from Heaven, she was the commander of Castiel's garrison, and their interactions onscreen give the sense that they were friends, or as close to friends as angels could be before she fell.
Her story, in a way, foreshadows Castiel realizing the value of humanity in later seasons. If he hadn't turned her into the angels' wrath, and if she hadn't been killed by Michael in season five, the two might have had the chance to develop their relationship with their mindsets more closely aligned.
Claire & Kaia
These two meet in the backdoor pilot of Wayward Sisters, a spin-off that premiered in season thirteen. Although they spend no more than 24 hours together, Kaia trusts Claire enough to go through the portal to the Bad Place to rescue Sam and Dean. Kaia's death at the end of the episode hit Claire hard, and she vows to find Kaia's killer.
In season fourteen's "The Scar," Jody makes the comment, referring to Claire and Kaia, "First love strikes quick," confirming fans suspicions that the two did share a brief romance. Unfortunately, the spin-off was not picked up, so fans will likely never know whether or not Kaia returns or if the two reunite.
Sam & Madison
The boys meet Madison on a hunt for a werewolf and discover that, unbeknownst to Madison, she is a werewolf herself. When they believe they have cured her of lycanthropy, she and Sam spend a night together. However, he wakes up with her standing over him, eyes yellow and teeth bared. When they track her down again, realizing the cure did not work, they have no choice but to kill her.
This took place in season two, before the point in the show where monsters, like Garth and Crowley, could be considered friends and allies, and before they discovered the real cure in season twelve, so Sam reluctantly complies, but we know now that she could have safely survived if the two had met today.
Dean & Pamela
Considering both Pamela's implied and Dean's proven promiscuity, and the fact that they were both initially attracted to each other when they meet in season four's "Lazarus," it was surprising that these two never hooked up. Even after the psychic is blinded while helping Dean figure out who pulled him out of Hell, she still agrees to help the Winchesters on two occasions before her death in season six.
Dean has a fiery personality to match Pamela's cool flirtiness, a dynamic that survives ten years later in her brief return to the show in Dean's "Nihilism" dream world, as she counters his "How come you always have a boyfriend?" with a "Why do you always want what you can't have?"
Naomi & Crowley
While their goals in the show are almost always in direct opposition, Crowley implies that the two spent some amorous time together in the days of Mesopotamia. Naomi is an angel who is sort of a bad guy; Crowley is a demon who is sort of a good guy. Their roles fit together naturally, and how entertaining a pair would the leader of Heaven and the king of Hell make?
They aren't a well-known pairing, but their interactions were enough to make fans wish they had seen more of them together. However, Naomi is believed to be killed in season eight, and by the time she returns five years later, Crowley had died. Since Mark Sheppard has stated he has no intentions of reprising his role, fans have little hope of the pair ever getting together.
Henry & Josie
It's true that Sam and Dean's paternal grandfather was married to their grandmother at the time of his death, but that didn't stop Josie from falling in love with him. In the season eight episode "As Time Goes By," Henry and the demon Abaddon, possessing Josie's body, enter Sam and Dean's time.
The next season's "Mother's Little Helper" reveals that the two Men of Letters operatives were on an assignment when Josie offered her own body as a residence for Abaddon so that Henry could continue living with his wife and young son. Henry is killed before he makes it back to his own time, and Josie is killed with Abaddon in season nine, but what could have happened if they had both survived the twenty-first century?
Kelly & Castiel
When Kelly is discovered by Castiel and the Winchesters as the woman carrying Lucifer's baby, they learn she will die upon the nephilim's birth. Castiel cares for Kelly as she lives out her final months, and the two grow to care for each other quite a bit.
If their relationship ever turned toward the romantic, one can imagine how differently things may have played out. Maybe they both would have been more inclined to try Sam's grace extraction idea, which would have allowed Jack to be born as a human, and therefore avoid killing his mother. He could have lived out his life with his mother and adoptive father as a product of Kelly's and Castiel's love.
Charlie & Kara
The Charlie Bradbury of the main world dies in season ten, but her counterpart of the apocalypse world, a world in which the Winchester brothers were never born and never stopped the apocalypse, appears and crosses over to the Winchesters' world three years later.
In "Optimism," she tells Sam the story of her and Kara, the cupcake baker she fell in love with who was killed during the apocalypse. Somehow, Sam and Dean being born prevented Kara from becoming a part of Charlie's life, so the Charlie in season seven had never met her, but if Kara had been introduced with Charlie, she could have been the beloved character's only long-term love interest.