The Five(ish) Doctors is seriously the best thing to come out of the 50th. Some theorise it is the only canon episode of Doctor Who ever. It has everything you could ever want and then so much more you never knew you wanted. Goddamn it is GOAT. Thank you based Peter.
You want Peter Davison? He made the damn thing.
Colin Baker? He squeezed out the front door to make it to this thing.
Sylvester McCoy? He ran away from The Hobbit™: The Desolation of Smaug in IMAX™ 3D to be in this.
Paul McGann? He wants in.
Christopher Eccleston? Well, no, but that's his problem.
Tom Baker? He's totally in this!
There are literally dozens of other surprise cameos, but I don't want to spoil any of them for you. Just that they will blow your mind.
Highly offended that Moffat refused to put them in the 50th, Five, Six, and Seven plan a daring adventure to get in the 50th. Along the way, they meet a whole bunch of people and generally talk trash about NuWho, but in a kind of loving way.
All in all it is probably the comfiest thing to ever come out of Doctor Who. 11/10, pure goaty basedness. In fact you are doing yourself a great disservice by not watching it right now. There is never a better time to watch The Five(ish) Doctors than literally right now.