What happens to Jenny, the daughter of the Tenth Doctor, after her single on-screen appearance in Doctor Who. In season 4's "The Doctor's Daughter," the TARDIS arrives on the planet Messaline, where the Doctor is promptly forced to yield a sample of his cells into what essentially amounts to a single-person reproduction machine, creating a fully grown-biological descendant of the donor. This process gives birth to Jenny, a retraction of "generated anomaly," and the Doctor begins to impart his morals and teachings to this newborn soldier. Despite the misgivings of others, Jenny asserts her independence as an autonomous living creature and begins to lean more towards her father's side than that of the army she was bred to serve.
As the Doctor reveals the truth of the Messaline war, Jenny takes a bullet intended for her father, and the TARDIS leaves mournfully, with the Doctor believing the young woman to have died after a short time in existence. In truth, Jenny regenerated after the Doctor's departure, oddly retaining the same face and form as her first incarnation. Jenny ran away from the place of her birth, excited to explore new worlds and meet new people, demonstrating the same adventurer's spirit as the Doctor. In an odd real-life quirk, Jenny was played by Georgia Moffett, the daughter of Peter Davison, who played the Fifth Doctor. Moffett would later marry and have children with her co-star, David Tennant. So, the Fifth Doctor's daughter played the Tenth Doctor's daughter and then went on to have a daughter with the Tenth Doctor. Wibbly-wobbly timey-wimey, indeed.
Despite various rumors and many calls from fans for more of Jenny, the character has yet to return to Doctor Who, leaving her adventures in time and space unknown. Fortunately, Jenny's story has been continued via the form of comic and audio adventures. Although Doctor Who's printed stories aren't necessarily canonical, the Big Finish audios have been confirmed thanks to "The Night of the Doctor."
Along with mostly every other past companion, Jenny is captured by Adam in Prisoners of Time as part of a grand plan to get revenge on the Doctor for dumping him from the TARDIS in season 1. Later, in the multi-Doctor "The Lost Dimension" comic, Jenny meets past incarnations of the Doctor while on a mission to save the universe and the Fifth Doctor from The Void. This comic also details Jenny's life immediately after leaving Messaline, during which time she repaired a Bowship to travel in and crafted herself a set of Gallifreyan armor before picking up a distress signal from Jack Harkness and setting out.
By far Jenny's biggest off-screen adventure, however, is the audio series Jenny: The Doctor's Daughter, for which Georgia Moffett (now Tennant) reprised her role as the genetically engineered Time Lady for the first time since her TV debut. Released in 2018, the four-part anthology begins with Jenny struggling to get to grips with piloting spacecraft and crashing into the company of recurring conman, Garundel. After splitting from the criminal, Jenny manages to create her own vortex manipulator-style device to travel through time and finds an assistant figure in Noah, mirroring her father's tendencies. In "Prisoner of the Ood," Jenny accidentally frees a criminal from Ood capture and puts the Earth in danger and the classic Doctor Who styling of "Neon Reign" sees Jenny and Noah free the planet of Kamshassa from a ruthless leader known as the Dragon Lord.
Around this time, Jenny and Noah procure a SporeShip, which is later named "Jenny One" and used to move between locations. The primary antagonist throughout these audio stories is COLT-5000, a cyborg bounty hunter who makes a deal with Garundel and chases Jenny from planet to planet. In the 2019 Fifth Doctor story "Relative Time," Jenny crashes into the Fifth Doctor's TARDIS, uniting Peter Davison and his real-life daughter in Doctor Who for the first time. Jenny has seemingly parted with Noah by this point, and it's revealed that she is unsure why the Doctor left her behind in "The Doctor's Daughter." The father-daughter duo work together to tackle a villainous Time Lord known as The Nine.
Doctor Who season 12 premieres January 1st 2020 on BBC and BBC America.