The Doctor Who 50th Anniversary Special, The Day of the Doctor, was filled with references to past episodes. There’s been a lot of posts attempting to list all these “Easter Eggs” and some are pretty extensive, but I think these two videos win for finding the most by far.
YouTube user Charlie, who runs the channel and blog Emergency Awesome has put together two videos that together must have in the neighborhood of 70 hidden references. Seriously, this guy has one heck of a keen eye for the hidden gems and a serious knowledge of Doctor Who history.
In part one he uncovers about 33-34 hidden bits.
The sheer number Charlie finds in part one alone is impressive, but I think he outdoes himself with part two.
To check out more cool and geeky stuff Charlie uncovers, check out the links to his various Emergency Awesome sites.