The Tenth and Fourteenth Doctor star David Tennant praises his successor Ncuti Gatwa’s performance in an interview for Variety
The Tenth and Fourteenth Doctor star David Tennant praises his successor Ncuti Gatwa’s performance in an interview for Variety
We don’t know yet.
Basically, 13 regenerated into Tennant again (changing clothes this time in the process which is unusual), and the Doctor reacts with confusion. That was the new years special last December. The specials this year will have Tennant again and explain why 13 regenerated into a familiar face. After the specials, Gotwa takes over as the official new Doctor
This seems to involve the celestial toymaker, who has the ability to alter reality.