I was totally half asleep when I watched that episode yesterday if I missed that. 'Cause god, that IS irrationally hot. ::seconds your sentiments::.

To bad he's wrong.
It's not the conditional, it's the past subjunctive, also called the irrealis.
Counterfactual "if I was" is standard English.

See, I also wondered if that should have been subjunctive.
But I think it might be a second conditional, as the sentence was only a fragment. I think it implies "[I would live on the moon,] if only that were possible."; where "I would live on the moon" is the main clause and "if only that were possible" is the second conditional clause.

It is the subjunctive/irrealis. But some sources, particularly ESL sources, call it the conditional as well. So I'll give him that.

Yes, I think I have seen it refered to in both ways. In Britain, terming it subjunctive is more common, but I think in America it's more often known as conditional? Still, Who is British, so they really should use proper Brit-speak.

There's no reason why it can't be both: a subjunctive/irrealis verb form in a conditional clause.
The Doctor was still wrong to correct him, tho.

So it is a conditional clause, but the reason that it should be "were" not "was" is that it's subjunctive, not that it's conditional. Hmm. I am tempted to write A Strongly Worded Letter to the BBC.

But there's nothing wrong with "If only that was possible." "was" still expresses the counterfactual nature of the statement. It's not ambiguous. Writers have been using "if it was" and "if it were" interchangeably for 400 years.

"be" is the only verb with a special form in the subjunctive/irrealis. With all other verbs, we use the simple past.

If only I had a TARDIS, I'd travel back in time.
If I lived in Cardiff, I'd work for Torchwood.

So with all verbs except "be", we don't need a special form. But some people insist that we have to use this special form "were" with "be", despite the fact that many writers and speakers of English don't.

I think "if it were" it the much more pleasing form though. It's interesting that "to be" is the only example of the special subjunctive form, I guess that's a reflection of its meaning. "Being" is a very abstract term, whereas other concepts like "having" or "living" are much more concrete. So "if I were" is a broader concept than "if I had", in that it describes a state of the world rather than a single fact like ownership.

Here's some more info, specifically the last 4 paragraphs
http://158.130.17.5/%7Emyl/languagelog/archives/005515.html

*isn't even watching and finds that hot*