While District 9 seems to have a case against racism and apartheid in South Africa, not all of its South African inspirations are political. Neill Blomkamp's aliens were also inspired by a common Johannesburg pest: the Parktown Prawn.

After the screening of District 9 in Johannesburg, many noticed the "prawns" - as the aliens are referred to by many humans - are a reference to Parktown Prawns, a common and loathed pest often found in Johannesburg homes. Parktown Prawns aren't actually prawns, but a species of king cricket that has likely been around since prehistoric times. The bugs can grow up to 10 centimeters in length, and are equipped with barbed legs and powerful mandibles.

But it's more than their name and appearance that the District 9 aliens don. One of the Parktown Prawn's features is its tendency to spew a nasty black sludge, which is probably the inspiration for the black alien liquid that's central to the movie's plot.

Human interactions with the prawns are also similar: you have to be calm, but firm.

[via io9]