Doctor Who Season 2, Episode 6 Reintroduces The Show's Most Mysterious Character
This article contains spoilers for "Doctor Who" season 2, episode 6 — "The Interstellar Song Contest"
Despite finding himself in the middle of the "Doctor Who" take on what the Eurovision song contest looks like in 2925, the Fifteenth Doctor (Ncuti Gatwa) isn't a particularly happy camper in "The Interstellar Song Contest." Much of this is because Freddie Fox's Hellion terrorist Kid invades the control room mid-party and quite literally empties the space station arena by opening the roof. If sucking 100,000 effectively dead contestants and audience members into the "mavity" bubble (the show has really committed to the gravity name change bit from the "Doctor Who" 60th Anniversary Special "WIld Blue Yonder") surrounding the station is bad, though, Kid's intention to kill over three trillion home viewers is something else entirely.
The problem is that before the Doctor can put a stop to this devious plan, he has to deal with the fact that he's one of the people Kid ejected from the station, and is freezing in space. Fortunately, he receives a little outside — or rather, inside — help in the form of a vision. The shocked Doctor sees an elderly woman calling to him from the inside of a sparsely-furnished TARDIS, calling him "grandfather" and telling him to wake up. The visions continue as the episode progresses, with the woman imploring the Doctor to find her and attempting to help him get a grip when he becomes furious and starts torturing Kid.
The Disney+ era "Doctor Who" has no shortage of mysterious women, with Anita Dobson's Mrs. Flood currently leading the strangeness parade. However, there's only one mystery lady who might have access to a TARDIS and who also refers to the Doctor as a grandfather: Susan Foreman, the First Doctor's (William Hartnell) granddaughter and companion.
Susan is a mysterious character from the show's early days
Susan (Carole Ann Ford) was an integral part of the show's very beginning and has featured in novels, comic books and so on, but hasn't been seen on the show proper in ages. Back in her day, "Doctor Who" was a simpler show where the Doctor and Susan had fled Gallifrey in a stolen TARDIS together, and regeneration wasn't a thing yet. To address this (and, in all likelihood, to avoid having to give Susan a clear timeline after the show established the Doctor's nature and made her presence as a blood relative difficult to explain), the vast "Doctor Who" lore has given us several Susan origin stories, and her true backstory is a closely guarded in-universe secret. More than just about anything else in the show, Susan's true nature is a giant ball of timey-wimey stuff.
Luckily, "Doctor Who" might be a long-running sci-fi classic, but it does try to embrace newcomers with handy explainers of the matters at hand and even occasionally drops hints at future events. As such, the Disney+ era has already done some light lifting to establish a more manageable backstory for Susan. In season 1, episode 7 — "The Legend of Ruby Sunday" — the Doctor established a theory that Susan is indeed her biological granddaughter, but in the Doctor's personal timeline his child (and Susan's parent) is yet to be born. The show has done nothing to contradict this line of thinking since, and with what seems an awful lot like Susan now establishing telepathic communication with the Doctor, it might just be that "Doctor Who" is finally preparing to unravel this mysterious First Doctor-era character's story.