From a special short 3-D adventure done as a charity fundraiser, one could not expect much in the way of storytelling. As evinced by The Five Doctors, specials designed to bring back as many beloved characters as possible don't always mean everyone will have something important to contribute. These stories must therefore be taken in the vein they are intended; as reunion episodes.
The plotline of this 2 parter is convoluted and ludicrous, but who cares! Its a chance to see something of Doctor Who back on the screen after an absence of several years. Perhaps the most satisfying moments include a long awaited meeting of the 6th Doctor and the Brig. Yates being back in the military is a nice touch after his redemption in "Planet of Spiders". There is also a certain charm with seeing different companions interact with someone other than their Doctor. Equally, it was nice to see old pairings reunited. John Pertwee particularly managed to get back with some old friends. It would have been nice if Tom Baker had been given an action scene, but beggers can't be choosers.
There were some aspects that could have vastly improved this short tale with minimum difficulty. The 3-D effects were passable, but the only thing really worth seeing in that aspect were the opening titles and the floating heads of the departed Doctors. Equally, the casts of the heads could have been better. It would have been nice if we'd been given something better to look at with our 3-D specs other than produce carts. If earth is the background there has to be something to liven it up. The story was non-existant, but as I said, a logical story seems too much to ask for a ten minute reunion piece. A vast improvement could have been made in costuming however. Apart from Ace, Mel, Sarah Jane and the UNIT crew, the companions wore clothing which did little to reflect the clothing from their travels with the Doctor. Even Leela was only given something vaugely tribal which was nothing near her original costume. Perhaps the most disappointing thing was the "you could influence the outcome" baloney. Viewers got to pick between two characters, Mandi or Ron, to help the Doctor. A "lucky" few have seen both versions. The disappointment...there's no difference! No matter who the viewers picked the same 3 second event happens. Liz is wrestling with the Rani, either Mandi or Ron pull Liz away from the Rani as if they thought Liz was mugging her or something, then the Rani points her gun at the "helpful" character and he/she runs off! Yeech!
As a whole its still a fun little watch, but just to see the old faces again.
Oh, and I love the technized theme tune.