As well as marking the final season with Peter Capaldi in the TARDIS and Steven Moffat as showrunner, season 10 of Doctor Who also saw the debut of a brand new companion in the form of Bill Potts, as played by Pearl Mackie. Fan reaction to Bill's debut episode 'The Pilot' was mostly full of praise for both the character and Mackie's performance, and with Matt Lucas' Nardole once again joining the cast, the show's central dynamic was given a very different flavor compared to Moffat's past companion combinations.
Both Amy Pond and Clara Oswald were undoubtedly fantastic characters played by great actresses, and they will surely be remembered fondly by Whovians for years to come. However, both the Pond and Oswald eras of Doctor Who were met with criticism - most of it directed at Moffat - concerning the considerable impact those companions were having on the overall story arcs, and the focus that was placed upon them.
Karen Gillan's Amy was perennially presented as a quirky and unique young woman with something indefinably special and other-worldly about her. Often, she was at the center of the show's mysteries and the onus would be on the Doctor to try and figure out why - whether it was the crack in her bedroom wall, her Time Lord pregnancy or being replaced by a Ganger.
Her successor Clara adhered to much the same mold. The Doctor was astounded to keep finding various incarnations of the companion in different periods of space and time, leading him to call her his "Impossible Girl". It was eventually revealed that Clara had entered herself into The Doctor's time-stream to save him from the Great Intelligence and thus was inextricably woven into the lives of all his regenerations.
Some of these companion-centric arcs were very successful - most notably the reveal that Amy's child was actually River Song - but there was criticism from some quarters suggesting that the focus had shifted too heavily onto The Doctor's assistants, with Clara in particular regularly threatening to become the show's main character. This issue was still prevalent as recently as the season 9 finale, 'Hell Bent', in which the return of big baddie Rassilon (played by Game of Thrones' Donald Sumpter) was swiftly glossed over, with the remainder of the episode instead dealing with whether or not Clara would cheat death - the answer to which was predictably ambiguous.
A Fresh Approach
Whether you were a fan of the 'enigmatic young woman becoming the Doctor's muse' trope or not, season 10 undoubtedly needed a new approach to the Doctor/Companion relationship. Enter Bill Potts.
Pearl Mackie's Bill is painted from the outset as the most ordinary of girls, albeit one with the kind of strong moral compass and inquisitive mind that makes her an ideal TARDIS occupant. Bill also faces the same kind of real-world problems someone in their early twenties would deal with: complicated crushes, a dead-end job, and lecturers protecting secret vaults (well, maybe not that one). Furthermore, it appears that The Doctor is Bill's first experience of all things alien and, consequently, her reactions to meeting Daleks, witnessing time travel and saving huge monsters lurking in the Thames are refreshingly honest and human.
To this end, Bill is highly reminiscent of the fan-favorite companion of the Ninth and Tenth Doctors, Rose Tyler. Like Rose, Bill is an ordinary person plucked from the British working class to witness the most extraordinary things the universe has to offer. Both characters are incredibly grounded and help to add a dose of humor to The Doctor's adventures.
Bill Potts appears to have been intentionally designed as the absolute antithesis of what came before her. She is as far as you can get from Amy and Clara without being, well, Nardole. She hasn't been plucked by the hand of destiny to bring The Doctor salvation, nor is she at the center of an intergalactic mystery that threatens the safety of the whole universe. Bill is simply us, the viewer. She performs the exact role that a companion needs to, giving the audience a figure they can relate to and allowing them to witness the alien world of The Doctor through a human pair of eyes.
That's not to say that Bill is merely a conduit for exposition. Far from it, in fact. In her four episodes thus far, Miss Potts has proved to be a character with personality, depth and excellent one-liners. However, she's a far simpler entity than Moffat's other two primary companions and crucially, exists outside rather than within the stories.