Rose and Martha for the character meme.
I will pick Rose, aaaaand this will turn into an essay that will probably make people angry. So be it.
My concept of writing Rose is entirely based on her behavior in Season 1, not thereafter. I think she went seriously off the rails as a character after that point. Because I’ll tell you this about Rose. She would kick the Doctor’s ass and drag him through the streets before she let him abandon Jack Harkness, whether he was alive or dead, on a satellite full of Dalek corpses. They had to write her out of character in order to make that story move, and it’s the original sin that got me connecting with her a lot less after S1. And I’ll tell you another thing about Rose. She would not try to pin down the Doctor to a domestic life and a mortgage, like she suggests in The Satan Pit. She loves the Doctor exactly as he is, a free spirit roaming time and space. She would not want him to be the kind of person who would want to settle down with her. The very idea that she would does a terrible disservice to the way she is able to embrace all of the Doctor’s personality, even the parts that aren’t always great, like his itch to always move on.
I spent the whole time watching Rose in S2 and the S4 finale wailing, “S1 Rose would never do this!!!”
Another important of Rose is remembering that she grew up poor. She always notices the humble people around her, the service workers and the vagrants. Her sense of justice is motivated by how her world was unjust to her. And there’s something in her that is eternally unsettled, I think, by how the Doctor never has to worry about money or where he’ll sleep tonight, or his ability to bluff his way into rarefied social spaces.
Along similar lines, Rose is always looking to improve herself. As a council flat girl she never got as many opportunities as she wanted to learn new skills and better herself. She’s proud of the accomplishments she’s made (gymnastics!) but she always wants more under her belt.