I have another suggestion from why-choose. Let's talk about habits. Compulsions. Stims. Whatever you want to call them. What are the mindless little things that Sam and Dean do? Those tiny little habits that maybe they don't even notice, but we sure do (and their brother definitely knows by heart).
- @schizosamwincester
SAM ORAL FIXATION MY BELOVED !! he is constantly chewing and sucking on things, has always been that way, he loves mints and sunflower seeds and toothpicks and all of that. he chews his nails too, which dean forces him to stop doing when he notices <3
(dean also likes putting his fingers--and other things--in sam's mouth when they have sex bcuz sam loves it so much <3)
dean needs to be constantly drinking something, likely from being used to drinking alcohol, but when he isn't drinking alcohol he's drinking soda, water, lemonade, anything he can find that keeps him sipping on something
dean fidgets a lot too, especially with his hands, he cracks his knuckles a lot, and it can drive sam crazy when dean doesn't have something to put his fidgety energy into bcuz dean will start bouncing his leg or tapping on something
also sam runs his hand through his hair alllll the time. he constantly is messing it up by doing this and when he is stressed he does it more or even starts lightly tugging on his hair, which dean also tells him not to do