Then there are the Slythereen, the aliens from the very first series (recently repeated on ABC2). When I originally watched it, I had just finished reading some moral theology lecture notes stating that our bodies are not ‘mere dress’. Then, there they were, literally hanging their human 'body suits' in the closet (in the Cabinet Room of No 10 Dowling Street, they'd been busy taking over England).
The Slytherin, you see, had faked a rather stagey crash-landing that destroyed Big Ben, and then proceeded to try and take over Britain by pretending to be the Prime Minister (and assorted overweight hangers-on) fighting the evil alien invaders. Their game plan was to stymie the fight against the invaders at the source, starting by neutralising all of the alien-fighting experts (and of course it might have worked if it weren't for the Doctor!).
The Slytherin’s masquerade, however, is made faintly ridiculous by their constant farting (a little matter-exchange problem with their body suits apparently). And they all look forward to taking off their body suits, so they can hunt in their true form...
And just as an aside, the episodes showing the Blair-esq Prime Minister Harold Saxon, who turns out to be the Doctor's old Nemesis, the Master, have some priceless moments.
The problem of evil and suffering
Dr Who has always, of course, been about the good old-fashioned fight between good and evil, albeit in the form of evil aliens. The new Dr Who, however, has added an underlying theme of the problem of evil and suffering.
The Doctor, it must be said, is neither all-powerful or all-knowing, but he does have that little blue police box that can go backwards and forwards in time - so why can't he go back and stop some of the great horrors of history from ever happening, his companions ask?
“ROSE: But it's not like I've changed history. Not much, I mean... he's never gonna be a world leader, he's not gonna start World War Three or anything...
DOCTOR: Rose - there's a man alive in the world who wasn't alive before. An ordinary man, that's the most important thing in creation. The whole world's different because he's alive.”