Doctor Who: 10 Things You Didn't Know About The Fourteenth Doctor
4. The Reason He Regenerated Into His Own Clothes
The second most notable thing about the Thirteenth Doctor’s regeneration was that her clothes regenerated with her.
This had only ever happened once before, when the First Doctor regenerated into the Second, with every subsequent Doctor inheriting their predecessor’s costume (and, in many cases, not changing out of it until the end of their debut story).
As such, fans were convinced that it would be part of a bigger plot – and we speculated about this a lot ourselves – potentially involving he Toymaker, given that he faced the First Doctor shortly before his regeneration, and would shortly be facing the Fourteenth.
However, in the end the explanation was much less complicated, with RTD simply wanting to avoid disrespecting drag culture. He said:
“With respect to Jodie and her Doctor, I think it can look like mockery when a straight man wears her clothes. To put a great big six-foot Scotsman into them looks like we’re taking the mickey.”
Your mileage on this may vary, but the decision was clearly well-intentioned, if a little odd, considering that Sacha Dhawan had worn the Thirteenth Doctor's costume literally in that same episode.
However it's understandable that you'd also want the first image of Fourteen to be him in his own outfit, given that he was only going to be wearing it for a year!