But, with the appearance of a previous Doctor alongside our current Doctor, this was about more than just (very recent) nostalgia. With its surprise multi-Doctor moment, “The Reality War” reminded us of one essential truth about the Doctor Who timeline: we’re only seeing a fraction of each Doctor’s life. Spoilers ahead for Doctor Who’s “The Reality War.”When Jodie Whittaker’s 13th Doctor strode into the TARDIS toward the end of “The Reality War,” it was perhaps the best-kept secret of the entire episode. The 15th Doctor (Ncuti Gatwa) meets the 13th Doctor (Jodie Whittaker). The adventures of Jodie Whittaker’s 13th Doctor (Seasons 11-13, 2018-2022) stream on HBO Max.