Oh, hello.” Those two words, from the person Ncuti Gatwa‘s Doctor regenerated into in the Doctor Who Season 2 finale, kick off a slew of questions we now have. Because that person? Billie Piper, very recognizable to fans as Rose Tyler,

And, of course, the 14th Doctor was played by David Tennant who ended up reuniting with Donna Noble (Catherine Tate) where he continues to live now after Ncuti’s version bi-generated out of him (which could come to play in a later theory…)