One key feature is the freedom to create a unique character within the 'Dr Who' universe. But a challenge could be staying true to the show's established lore and tone.
The key thing is getting the balance right between your OC's story and the existing 'Dr Who' narrative. A big challenge is ensuring your OC doesn't overshadow or disrupt the show's beloved elements. You have to respect the show's canon and build on it in a meaningful way.
The main feature is that you can bring a fresh perspective with your OC. A challenge might be making your OC fit seamlessly into the complex time-traveling plot of 'Dr Who'. Also, you need to capture the essence of the show's characters and their interactions.