Neither of these links are technically about writing, but both are about character and character development.

Sporkchop is doing an A to Z blogging challenge (because he likes to work much harder than I do) that is primarily focused on creating good villains, heroes, and tertiary characters. His blog is about Dungeons and Dragons, so there's a lot in there about rolling dice that you can ignore, but what he's trying to do as a dungeon master is to create an emotionally engaging fictional world with believable characters and a satisfying plot line. Hopefully that's a familiar set of goals for you.

This is a post from the Comics Curmudgeon that contrasts the way a character in Mary Worth responds to events to the way someone in real life would. (Here's the character's background, if you care.) Just like with Mark Trail dialog, I think it's really useful to study stuff that's laughably bad, figure out the thought process the writer went through to get there, and try to avoid that trap in your own writing.