Summary
- Tales of the TARDIS creates the possibility for unlimited adventures for past Doctors and companions.
- The new series explains how these stories are possible by introducing the concept of different timestreams, allowing for the return of previous Doctors after their regeneration.
- The creation of a multiverse in Doctor Who means that any past Doctor can be brought back without impacting the main storyline, opening the door for new spinoffs centered around the Doctor.
The Doctor Who spinoff Tales of the TARDIS sees the return of three Doctors and nine companions across six episodes. Tales of the TARDIS edits together classic Doctor Who serials with new scenes from the original cast to create the new series.
Tales of the TARDIS mainly revisits past adventures, but the new material at the start and end of each episode provides new information about Doctor Who's companions and what happened to them, as well as the fates of past incarnations of the Doctor. The episodes “Earthshock," “Vengeance on Varos," “The Curse of Fenric” are the only Tales of the TARDIS installments to feature the Doctor while “The Mind Robber," “The Three Doctors," and “The Time Meddler” use the companions reminiscing to revisit the Doctor’s adventures. This new addition to the Whoniverse is especially exciting because Tales of the TARDIS makes sure to explain exactly how these stories are possible.

All 26 Easter Eggs In Doctor Who's Tales Of The TARDIS By Episode
As the new Doctor Who spinoff Tales of the TARDIS makes its debut, eagle-eyed viewers will be able to spot various references to the Doctor's past.
How Doctor Who's New Spinoff Explains The Return Of Past Doctors
Previous Doctors returning to Doctor Who has always been momentous, with actors or old images of the character also being used in the Doctor Who 50th anniversary special. However, that was done by revisiting the Doctors in their own individual timelines. Tales of the TARDIS and the Doctor Who 60th anniversary specials are unique because they bring back previous Doctors after their regeneration, Tales of the TARDIS even suggests the Doctor does not need to regenerate and can grow old instead. Fortunately, in “The Curse of Fenric," the Seventh Doctor explains exactly how timestreams are the reason for the Doctor remaining unchanged.
The Seventh Doctor implies there are many different timestreams, or timelines, so the one he is living in with Ace, without regenerating, is completely different from the one in which the events of Doctor Who are taking place.
In “The Curse of Fenric”, the Seventh Doctor (Sylvester McCoy) reunites with his companion Ace (Sophie Aldred) to their battle against an ancient evil where a Viking curse brings the dead back to life in World War II. Explaining how he got old, Seven tells Ace, "Timestreams are funny things. In some, I regenerate. In others, I don’t. It’s all a matter of perspective." The Seventh Doctor implies there are many different timestreams, or timelines, so the one he is living in with Ace, without regenerating, is completely different from the one in which the events of Doctor Who are taking place.
Doctor Who Can Now Bring Back Any (& Every) Past Doctor
Tales of the TARDIS has essentially created a multiverse, which means any and every past Doctor from Doctor Who can be brought back. Multiple timestreams existing for each Doctor means one-off adventures or long-running adventures can be created without impacting the canon of the main Doctor Who storyline. Doctor Who has shown how much it wants to bring some classic characters back into the Whoniverse since the Companion Group was shown in the episode “The Power of the Doctor." Now, with every Doctor Who episode from the classic and new series on BBC iPlayer, audiences have a chance to reconnect with past Doctors before more spinoffs are created.
Showrunner Russel T Davies has indicated the Whoniverse will be expanding much more upon his return, which is already happening with new adventures such as Tales of the TARDIS and the multi-platform Doctor Who project Doom’s Day. Until now, Doctor Who spinoffs have mainly focused on characters in the Doctor Who world but not the Doctor directly, as in the case of the series Torchwood. However, the timestream creates the opportunity to have more Doctor-focused spinoffs where any of the previous Doctors can return and be the main character of their story.
All episodes of Tales of the TARDIS are exclusively available on BBC iPlayer.

All 12 Doctor Who Characters Returning For Tales Of The TARDIS
The new Doctor Who series Tales of the TARDIS gives several classic-era characters a chance to get closure and reminisce about their adventures.
Doctor Who Officially Rejects De-Aging Classic Characters For New Adventures
The timestream explanation also means Doctor Who has officially rejected de-aging classic characters for new adventures. David Tennant’s return raised questions about de-aging in Doctor Who as his last appearance as the Doctor was 10 years ago, and he looks visibly different from when he played Ten. Reasons have arisen that suggest he looks different because Tennant is playing the 14th Doctor, not the 10th, in the 60th anniversary special. Others believe that aging will just be ignored because de-aging in movies and TV can often look terrible, so it is not worth using it in Doctor Who.
Tales of the TARDIS has now confirmed that de-aging will not be used at all in Doctor Who, which will instead celebrate the classic characters' aging. Doctor Who’s rules around regeneration have often been tricky, as a Time Lord is only supposed to be able to have 12 regenerations and there are now more, but timestreams allow regeneration to not happen at all, or only some. This means the Doctor can regenerate back into a past version or have new adventures with an aged face without creating any plot holes. The timestreams explanation is a fantastic way to explore multiple Doctor Who spinoffs using already beloved characters.