Companions. As the character the audience is meant to relate to (supposedly!), and the entry point to the Doctor's crazy, manic world, they often end up being the heart and soul of the programme. They end up loved by millions, despised by some, and generally becoming a key part of the show's rich history.
The role of companion can often catapult an actor to another level. For example, Billie Piper and Arthur Darvill are now instantly recognisable television names and Karen Gillan has started a fledgling career in Hollywood.
They have to put in a lot of work, though. Being the audience's viewpoint means they often have to put in top notch performance after top notch performance. They have to make green screen seem like monolithic spaceships, costumes seem like threatening alien races and small streets seem like ancient cities by reacting to everything just right. And on top of that, they have to bear in mind the ambitious arcs and storylines the showrunners come up with for their characters.
It's time to celebrate that work and the number of talented performers who have travelled on the TARDIS with a countdown of the 10 best companion performances in NuWho. So buckle up and enjoy the show!