Over the past three weeks I have been watching a lot of Doctor Who — which I discussed starting here — and I am currently in the middle of the fourth season. David Tennant is still going strong as the Doctor, and the companions have changed a number of times now.

Knowing what’s to come in the future with Matt Smith and subsequent companions, coupled with all the changes that have already taken place, I have been thinking more and more about how daring of a series Doctor Who really is, and how brilliantly flexible the universe has been written.

Though I find few episodes to be lacking in imagination or only partly compelling, it has occurred to me at times a series like this — very episodic in nature — could run the risk of becoming stale over time. Despite this, however, the changing of cast keeps it fresh before it even gets close to its expiry date.

Tennant is still the Doctor where I am currently, yet the change of companions alone has made a big difference in the interactions between characters. With newer companions like Martha Jones and Donna Noble the Doctor is challenged in ways he wasn’t with Rose, especially in the case of Donna. Martha presented a companion that was more competent than Rose in many ways and more openly affectionate toward the Doctor, yet she had feelings he just couldn’t reciprocate. So, though he was very fond of her, she compromised how he wanted to go about his travels after losing Rose.

Donna I find to be particularly interesting because of how much she manages to one-up the Doctor. While he is still brilliant, as you would expect, her more abrasive and assertive nature made for such a refreshing dynamic that it actually played a big part in the inspiration for this post. While many other companions have been more in awe of him and seem to feel they are in his shadow at times, Donna does a great job of humanizing him by calling out his flaws or ideas she doesn’t agree with, all the while hardly batting an eye.

With the eventual changes of casting with the Doctor in upcoming seasons as well, the shift of character and experience viewing will only be more dramatic. It has created a fascinating world where the protagonist in many ways becomes an entirely new person, yet still retains all of the memories and experiences of who they were before.

It is rather startling to consider that the characters (and actors) first introduced in the season in 2005 are now completely different — which I know doesn’t even scratch the surface concerning how many changes have happened. The status quo is constantly in flux, and that is what I find so special about the series, and why I consider it brave. So much of media seems concerned with making sure the status quo is never disrupted too much, yet this show will unabashedly change so much that the audience comes to love so strongly, only to make them fall in love all over again.