The final 60th Anniversary special for Doctor Who, "The Giggle," ends David Tennant's nostalgic return as the Doctor. However, this installment especially highlights how bringing back Russell T Davies' favorite Doctor is about much more than memories and warm feelings of series past. The ultimate result of his regeneration -- or in this case, bigeneration -- is about helping the character deal with his (and her) traumatic past(s). As the first woman to play the Doctor, Jodie Whittaker's turn in the TARDIS was bound to be controversial with fans' whose thinking is as stuck in the past as the time-machine's chameleon circuit.
Source：https://www.cbr.com/doctor-who-bigeneration-david-tennant-nostalgia/
