There were two other specials, less official in nature, that were nevertheless absolutely delightful and I think my favorites overall. I'll write about the Peter Davison comedy short and move on to The Light at the End audio play.
Peter Davison, as 5th Doctor, was known to me as Celery Guy in my youth when I stole occasions to watch Doctor Who on PBS in English and usually never managed to watch an entire serial. It turned out in the end that Celery Guy was only slightly less insane as a person than Tom Baker, which gives us a nearly endless series of grumpy and/or funny and/or wacko quotes. His recent diatribe on why there should not be a female Doctor being a case in point, marrying illogic and entitlement beautifully. Suffice it to say that I find him hilarious. His history with Doctor Who also didn't end with his dismissal. His daughter Georgina Moffett played Ten's daughter in The Doctor's Daughter, fell in love with David Tennant and married him. They have a child and everything. With all this meta happening, and rumours going around that all the living Doctors would appear in The Day of the Doctor, something was bound to happen.
What happened was The 5(ish) Doctors Reboot. I do not want to spoil this short, but it is extraordinarily funny. It stars Sylvester McCoy, Colin Baker, Peter Davison, Paul McGann and Tom Baker (ish), in which they try to be a part of The Day of the Doctor. I will leave it there. Watch it. Moffett, Tennant, Smith, Moffat and others, also appear.
It would not have been a proper 50th Anniversary celebration without a proper Big Finish audio play. They were responsible for continuing the adventures of most of the Doctors after their dismissals from the show and from the 1980s on were, lets be frank, the only good source of Doctor Who material out there. Big Finish made Paul McGann as the 8th Doctor and The Night of the Doctor would simply not have been possible were it not for Eight's adventures (most of which were great and are now cannon!). Their contribution to the 50th Anniversary was The Light at the End, starring all first eight Doctors, though primarily the living ones, Sylvester McCoy, Colin Baker, Peter Davison, Paul McGann and Tom Baker, and their (living) companions (i.e. no Sarah Jane). Something happens on 23 November 1963 to ordinary, everyman Bob Dovie that affects all the first eight doctors in a capital way. Time is collapsing unto itself around the Doctors and they must work together to solve the mystery, save Dovie's family and themselves. Of course, the Master is involved. If you are familiar with the voices of the classic Doctors, this thing is very fun. If you are only familiar with Nu Who, you might have a harder time sorting everyone out. This said, as with most Big Finish Doctor Who productions (and there are a gazillion of them) The Light at the End is a very good Doctor Who episode and the reunion many fans was hoping for.