I've said many times, and will say again, the one person I'd have moved heaven and earth, and sold my soul to the devil to get in the 50th, if I was in charge (or believed in souls) is William Russell as Ian Chesterton.
He's the only classic series actor/character you need.
I completely agree. I've been saying for ages how awesome it would be for old Ian to appear alongside the young looking Doctor (first Tennant, then Smith). The juxaposition would be interesting, especially to see Ian's reaction to the more hyperactive Doctor as oppose to his Doctor.
Alas, it seems we have to settle for a cameo appearance in An Adventure in Space and Time
Well, while they were doing that AAiS&T cameo, you never know, they may have filmed a little something extra for the Anniversary Special. It would be most awesome to see him, since he's the earliest cast member of the show still alive (Aside from Carol Ann Ford, who will hopefully be with us for quite some years to come) and it would almost be a crime not to include him in some capacity.
One Day I hope to be the Man my Cat thinks I am
Where are we going? And why are we in this Handbasket?