6) Deep Breath
“Deep Breath” isn’t an obvious contender for the status of ‘multi-Doctor story,’ but it definitely is one. Peter Capaldi’s introductory tale from back in 2014 took the newly-born Twelfth Doctor and Clara (Jenna Coleman) to Victorian London where they team up with their old pals, alien detectives the Paternoster Gang, to foil the plans of a creepy semi-organic robot the Half-Faced Man.
The shadow of the Eleventh Doctor lingers over the episode, as Clara has a hard time coming to terms with the Doctor’s severe change in age and personality. However, she’s finally able to see that he’s the same man underneath it all when Matt Smith himself appears. In an emotional closing sequence, Clara gets an unexpected phone call from the Eleventh Doctor (calling from before he regenerated), asking her to stay with him through this difficult time.
Some fans criticized the inclusion of Smith’s cameo, arguing that it overshadowed Capaldi’s introduction as the new Doctor, but you can’t deny that it’s great seeing his predecessor again and the Eleventh Doctor and Clara’s chat is the emotional core of the episode. Not a typical multi-Doctor story, then, but a great outing of Who nonetheless.