I love stories that do a good job of looking at the childhood or youth of the adult characters that I know and love.

YES. "Teeth of the Hydra" comes to mind, actually. Although, you know, I have very set ideas of what I think certain characters were like when they were kids, and it's hard to think differently, but a good writer can sell me. And, oh God... HCL HS fics. DAMN. Now I want some, badly.