Trivia: The topic of xenophobia runs strongly throughout the film. This is a very real issue for South Africa as evidenced by the xenophobic violence in early 2008 where approx. 30 foreigners living in South Africa were murdered and hundreds left injured and/or destitute. In fact there are still displaced foreigners living in homeless shelters, churches, etc today.
Trivia: There have been protests against the alleged stereotyping of Nigerians in the movie. Two of the more sensitive issues are the Nigerian prostitutes soliciting 'prawn' customers; and the character name Obesandjo (which is closely linked to the former Nigerian President's name Olusegun Obasanjo).
Trivia: The 'prawn' design is based on an actual giant cricket species, the mole cricket, found in suburbs of Johannesburg. Commonly known as 'Parktown Prawns', they can grow up to 20cm (8in) in length.
Trivia: The alien languages and sounds were created by rubbing pumpkins together.
Answer: That's more of a side effect of the fluid. See, only the Prawns could use their technology; it was "genetically activated", so to speak. So the fluid which powers their tech is like Prawn-gene concentrate. When Wikus was sprayed with the stuff it affected his genetic makeup.
Phixius