Quick, name a hit movie from South Africa. Until now, the only name likely to come up was The Gods Must Be Crazy, the 1980 comic saga of a Bushman whose life is disrupted by a Coke bottle tossed from a plane.

That sleeper success has almost nothing in common with District 9, a science-fiction film set in modern Johannesburg from 30-year-old first-time feature director Neill Blomkamp. For one thing, District 9 benefits from all the marketing muscle of Lord of the Rings impresario Peter Jackson. (After Jackson recruited Blomkamp for a big Hollywood project that fell through, he offered to produce the commercial director’s own script as a consolation prize.) Gods didn’t touch the most contentious topic in South African politics of its day, whereas District 9, which was largely shot in the bleak landscape of Soweto, is built on an apartheid metaphor. Then there’s the fact that one film is a gentle, absurdist romp, the other a blood-spattered action drama shot in the seat-of-the-pants style of 28 Days Later.

But for all this, the two films do share a secret weapon: They go back to basics. Critics hailed The Gods Must Be Crazy as a return to classic slapstick in an age of bloated, high-concept comedies. Similarly, in a genre where budgets and plots tend to spiral out of control, District 9 has an easily summarized story and visual effects that illustrate it: no more, no less. It’s not particularly original. (The core concept — extraterrestrial asylum seekers land on Earth and become second-class citizens — was explored in the 1990s Alien Nation movie and TV series.) But, by virtue of the director’s solid choices, the movie succeeds in making audiences give a damn where more ambitious Hollywood efforts have failed.

The film opens with pseudo-documentary footage of first alien contact in the early 1980s. A mothership hovers over Johannesburg — essentially the world’s biggest backyard wreck, because its huddled masses of passengers don’t have pilots’ licenses. Human-sized, with insectoid heads, clicking speech and crustacean claws, the aliens are derisively christened “prawns” by the natives, who have no desire to share their city with this baffling, sometimes brutal race.

The newcomers are policed by a private contractor, Multi-National United, and herded into a shantytown called District 9, where they become Johannesburg’s lowest of the low. But when humans still complain about the undesirables’ crime and scavenging, MNU gears up to relocate them, by force if necessary.

It sounds like a setup for one heavy-handed political allegory. But, like Korean monster flick The Host, District 9 benefits from pivoting on a character who’s basically a buffoon. As Wikus van der Merwe, the hapless MNU operative assigned to oversee the relocation, Sharlto Copley initially comes off as an Afrikaner version of Michael Scott from “The Office.” He’s cluelessly glib and cheerfully pompous about his job, whether he’s torching a houseful of alien eggs or plying a cute little “prawn” with candy. No matter how ugly his tasks, this company man does them with a big smile on his face for the camera crew … until he’s exposed to an alien substance that starts changing him physically. Then Wikus finds himself with no choice but to empathize with nonhumans, and the audience takes a harrowing journey with him.

Copley’s serio-comic performance is a weird choice for this sort of film; according to Blomkamp, the first-time actor developed the character in sketch-comedy style, improvising all his dialogue. Yet the result is a protagonist whose plausible, fallible, perversely likeable humanity is never in doubt, even when he picks up a big gun and goes Schwarzenegger. By the last third, we’re rooting for him to shoot it, too.

There are bones to pick with District 9. Blomkamp jumps in and out of the mockumentary conceit whenever he feels like it, and the shifts to obvious fiction can be jarring. Certain key facts about the aliens remain murky: If they possess super-weapons only they can use, as we learn early on, why haven’t they mounted an organized resistance to human oppression? (Blomkamp offers a decent explanation for this in interviews; too bad he didn’t figure out how to do so on-screen.) Physical transformation scenes reminiscent of Cronenberg’s The Fly will freak out some viewers — and thrill others.

For a movie rife with violence and disturbing imagery, District 9 has a guiding spirit that’s surprisingly sweet and even hokey. But that’s part of its charm. If Spielberg’s E.T. had been greeted on the landing pad by Homeland Security, his story might have gone something like this.