Head Canon You Never Shake

This isn’t intended to codify anything: I’m just curious about what little details always influence your portrayals of certain characters that just make sense to you but may never actually show up in the story (or any story).  Basically, I’m curious if other people fixate on little background details as strongly as I do. This being tumblr, I’m certain at least some of you do.  Also, if I really like something, I might have it off of you, if you don’t mind.  Add one to the list and pass it on.

1. In my Supernatural fics, Ellen Harvelle’s maiden name is always ‘Longabaugh’ because I’m convinced she’s a direct descendant of Harry Longabaugh (aka The Sundance Kid) and Etta Place.