Honestly I'm shocked they caught on to him. The last time I went through Passport control in Joburg (while leaving the country) the situation was thus:
> Four workers. 3x males, 1x female
> one male flirting with female, not at his station
>one male reading newspaper, while at his station
> One male, seemingly engaged at his station.
If he'd presented his American passport, he probably would have got through. Whatever a "World Passport" is, i'm sure it doesn't even look legit.
South Africans are weird about permanent residency. There are a large numbers of foreigners who live there part time or full time, however, and I'm sure some sort of extended non-working visa is available.