But if Piper does end up becoming an incarnation of the Doctor, there’s very much a good precedent for it. Fast forward to the very next serial, in September 1979, and the Doctor is baffled as to why Princess Astra is suddenly back, when it's revealed that this isn’t Princess Astra at all. The 4th Doctor (Tom Baker) and Romana (Lalla Ward) surrounded by Daleks in 1979. Rcc/ShutterstockInstead, Romana has regenerated and specifically chosen to look like Princess Astra. Later, of course, Baker became the 6th Doctor at the end of “The Caves of Androzani” in 1984.