Doctor Who: 20 Things You Didn't Know About The Day Of The Doctor
4. David Tennant's First Scene Was His First Day On Set
David Tennant doesn't appear until 20 minutes into the episode, riding out of the TARDIS on horseback, accompanied by good old Queen Bess. Oh, and he's also hunting down a Zygon - because the Doctor doesn't take days off.
This scene was also Tennant's first day on set, with the actor donning his iconic costume for the first time in roughly four years.
Producer Marcus Wilson said that it was like "live archive footage". Truly, it must've been both bizarre and brilliant to have Tennant playing the Doctor again!