Whosday: Susan Foreman

Because the show Doctor Who was never meant to be exclusively about the Doctor, it naturally meant that his earliest companions were all fleshed out, and who better to talk about than the very first onscreen companion, Susan Foreman?

Susan was the pseudonym of the Doctor's granddaughter, back when the Doctor was basically meant to look even more elderly than the actor playing him was, and not the reverse (to the point where William Hartnell always wore a wig and sometimes a cap to conceal his hairline in order to make his Doctor look old), and so it would not have seemed strange at all that the Doctor had a granddaughter.

The 1960s was also probably the most emotionally mature decade of the show (in a similar fashion to how the 1970s was perhaps the most intellectually mature decade of the show, but that's a whole other article) until the revival in the 21st century, and thus that meant that there was sometimes interpersonal conflict, and there was sometimes strong sentiments towards other characters.  Susan often expressed this the most, seeing the world with young, innocent eyes in contrast to the more paranoid and cynical worldview of her grandfather, the Doctor, and so they often clashed, such as when she did whatever she could to defend the innocence of her Earth teachers, and later the Sensorites.  

She was also, being essentially the youngest of the TARDIS team, was often depicted as the most vulnerable both physically and emotionally, often needing rescuing by both of the Doctor's other companions, Ian Chesterton and Barbara Wright.  However, unlike Ian and Barbara, Susan's personality was not always too terribly fleshed out, depite how emotionally mature the show was and how much effort there was into making Ian and Barbara multidimensional.  However, given that Barbara was a highly complex character, this probably has almost nothing to do with Susan being a girl, and everything to do with how young her character was, especially when one takes into account that the most clearly defined personality traits of Susan were her insatiable curiosity (a trait she may have gained from her equally inquisitive Grandfather), general lack of guile, stubbornness (a trait she also shared with her grandfather), strong sense of justice towards the innocent, and her morbid sense of humor (also a trait of the First Doctor's).

However, this article desribed Susan's personality and her role in the show, not her history.  To learn Susan's history, I suggest you watch this video: