It had to happen: invading aliens are now the good guys.

Hollywood loves to turn the tables on its own hackneyed formulae. For decades, Native Americans were on an endless warpath in the movies, getting up in the morning with only one item on their "to do" list: namely, mount yet another attack on gnarly ranchers and the occasional wagon train.  But these days, the Indians in the popcorn palaces are laid back: sage and sympathetic.

Overturning clich's always plays well, because doing so allows filmmakers to meld helpful familiarity (you know how these guys are supposed to behave) with surprise (they're not conforming to type).   

In District 9, a hubcap-shaped alien mother ship looking like a kit bash of a few thousand Revell model tank parts comes to Earth and stalls over Johannesburg. The confused occupants disembark, and quickly confront their South African hosts with yet another social problem (as if the country needs one).  Where do we put these dudes?

The South Africans respond with a nod to history by stuffing the aliens into a massive camp in the bad part of town: Soweto for extraterrestrials. The accidental tourists multiply like rabbits, and after a few decades turn their township into a really unattractive neighborhood.

Attempts to deal with the aliens (read: get them out of everyone's hair) become the day job of a stumbling Afrikaner (played by Sharito Copley) a bureaucrat who's in the employ of a massive, and manifestly malevolent, defense contractor. The mixture of innocence, danger, and squalor is at first confusing; ten minutes after the opening titles, you think you're watching Borat meets "Blackhawk Down".

The social commentary in District 9 is about as obvious as Vin Diesel in a Munchkin bar, and reviewers have had a nice time trying to figure out the political intent of the film.  But what about the alien angle?  Is it realistic to think that a passel of extraterrestrials could really get stranded on Earth, confronting us not with havoc and destruction, but with a far more prosaic problem: accommodation?

Probably not. These guys cause social problems only because they're pretty much like us.  Sure, physically they're a bonkers blend of Ray Harryhausen skeleton warriors, oversized lobsters, and that tentacled Davy Jones character from Pirates of the Caribbean.  With more mouth parts than a bag full of grasshoppers, these guys aren't attractive. Unlike the smooth, calm-and-collected grays that entice Scully and Mulder, the aliens in District 9 are upright crawdaddys.

What's hard to swallow about these extraterrestrials-in-residence is that they think like us, share our emotions, and even have the same body gestures. And while they're technically capable of a few things we're not - interstellar travel comes to mind - they're not obviously more advanced.  We can even operate their rockets and weapons, although you have to sport a bit of alien DNA to do this (an idea reminiscent of a long-ago proposal that would use biometric sensing to limit the use of handguns to legitimate owners).

Bottom line: if you could get over their fruit de mer appearance, you might sit next to these District 9 residents on the bus.

All of which makes them comprehensible and ultimately sympathetic. But trust me, real aliens will be real different. They won't have DNA that can mix with ours, they won't enjoy dining on cat food, they won't have technology we can instantly operate, and they won't be like Neanderthals  - just another species that's pretty similar, but not similar enough to get along.

That's a mistake that Hollywood makes repeatedly: the anthropocentric view that aliens, if they'd only dress better, could pass for humans.  Filmmakers must adopt this point of view, for otherwise the aliens would be, well, too alien.

District 9 breaks new ground by condemning alien invaders to a degrading, ghetto existence.  It's undoubtedly a long way from reality, but then again, so are the aseptic grays who come to Earth in immaculate, polished spacecraft with no more subtlety of intent than to probe our privates.

It's nice when the bad guys can occasionally get out of character.