When I first watched it as a teenager, I didn’t enjoy The Thing. I can't really recall what it was I didn't like about it, but I seem to remember finding it a little confusing and I can remember not being a fan of the special effects (some would consider that last statement heresy). But since then, I’ve come to like it a great deal. I wouldn't place it at the top of the genre like some people would, but it wouldn't be far off.

First things first, I appreciate the special effects a lot more now. I think the problem when I first watched it was just how bizarre it all was. Tentacles? Bloody flower guts? Giant snapping mouths? Maybe I found it hard to suspend my disbelief, or perhaps I found it repulsive – I don't mind gore in horror films, but I'm not a fan of what I'd call 'gloop'. For some reason I can happily watch limbs get blown and sawn off, or see people get shot, stabbed and eaten, but my sick trigger is sensitive to 'gloopy' film monsters. For instance, I love David Cronenberg's version of The Fly, but I do actually come close to gagging when watching it.

So perhaps I didn't appreciate the special effects for those reasons. But they're actually pretty great. One of the best bits has to be when an imitation human head sprouts a tentacle from its mouth and pulls itself along – and earlier on when the head begins to detach itself from its body. It's nasty and unpleasant and great to watch. And then there's the bit when Palmer's face rips apart and a giant alien mouth sprouts and bites a guy in the head. Sweet. (And to make it even better, the man who's getting bitten is shaken from side to side like a rag doll.)

But not all the special effects work great. Although I love the head being ripped off and I love it when it shoots a tentacle from its mouth, it does look silly rather than disturbing when it sprouts antennae and spidery legs. There's a fine line between great and crap. And the bit at the end isn't particularly impressive either – the bit where we see huge tentacles and a massive monster. It's overkill and the effects don't match what has come before.

Much better are the little bits. Right at the end, right before the silly tentacle business and the unconvincing alien dog, is a bit where Garry encounters an assimilated Blair and Blair sticks his hand in his head. It's brilliantly done. And then after that you see Blair dragging Garry along by his face like he’s sack. Again it's sick and nasty, but in a much more believable way.

However, it's not the monster that makes The Thing such an enjoyable film. It's the confusion and the paranoia that its presence generates in the humans (I guess when I first watched it as a kid, I didn't realise that confusion was the point – it’s kind of a take on the AIDS crisis). After all, seeing as The Thing is a shape-shifter, and it can take on any form, everyone's a suspect – anyone could be a carrier.

This climate of paranoia and suspicion is best illustrated in the scene where MacReady (Kurt Russell) ties the surviving scientists and workers to chairs so that he can check their blood to see who's human and who's not (it’s like a homemade AIDS test). The scene really is tense, as you haven't got a clue who's been assimilated and who hasn't. You're not even sure if MacReady is who he says he is, as even he's been built up as a suspect. But it literally could be anybody and the scene's a powder keg.

Another great scene is when MacReady declares that he knows for certain he's human and the camera slowly pans across the rest of the group. Do we believe him, and who among the group isn't what he says he is?

As well as these nail-biting scenes, I love the creepy moments too (they're often a lot better than the 'scary' bits). My favourite is when a half assimilated Bennings is caught trying to escape the camp – he's almost a perfect copy but his hands are deformed – and he lets off an eerie howl before he's burnt to a crisp (there are a lot of torchings in this film, which, needless to say, I love – and one brilliant torching is immediately followed by an exploding). And there's also the bit where MacReady visits Blair, who's been locked in the tool shed. MacReady opens a slit and Blair's sitting there by a noose while eating cans of food. He then begs to be let out. He insists that he's much better. It's a superb scene. And as simple as they are, I love all the lingering shots of the dog. It's a creepy mutt. It's got a thousand yard stare.

Also rather creepy is the ending. After all the pyrotechnics, MacReady thinks he's the sole survivor. But then Childs shows up. Childs’ explanation is that he got lost in the snow. There's a bit of an awkward conversation, and even though Mac kind of knows that it isn't the real Childs, he's become resigned to his fate and shares a smoke. It's an ending that, in the best way, keeps you wondering.

And on a final note, I must say how much I enjoy Mac's snow-sombrero and his bad geography. "Hey Sweden!" he shouts when he visits a Norwegian camp. There aren’t many laughs in the film, but the ones that are there do the trick.