In Nov. 2023, David Tennant returns to Doctor Who in an unprecedented move for the sci-fi series. While past Doctors have returned before, and "The Day of the Doctor" may have fleetingly featured Tom Baker as a new incarnation of the Doctor, this is the first time that a former Doctor Who star has returned to play a new incarnation as the series' lead. Jodie Whittaker's final episode, "The Power of the Doctor," ended on the surprise reveal of Tennant's return, when the Thirteenth Doctor's regeneration resulted in the Doctor gaining a familiar face. However, this isn't the return of the Tenth Doctor.
Source：https://www.cbr.com/doctor-who-fourteenth-doctor-different-from-tenth/
