headcanon: Jo and the Winchesters
It’s my belief that Sam developed a crush on Jo when he and Dean spent two weeks with the Harvelles when Sam was 10 years old. He and Jo spent their days building pillow forts, and hiding from Dean in the treehouse Bill built for Jo at the back of the Harvelle property.
Sam and Dean didn’t remember those two weeks until years after Jo and Ellen died. Sam’s sure that she remembered, and he’ll always regret that he didn’t until it was too late.