A white man comes from England to South Africa. He is looking for a hotel but all the hotels are full so he makes up his mind to try out a hotel for blacks. They have beds all right, but there is one problem: under the law, a white man cannot sleep in a blacks' hotel. Since it's getting late in the night, the receptionist has an advise to offer:
"Take this shoe-wax, rub it into your face, neck, and hands - so that nobody could tell you from a black - and I'll give you a bed for one night. I'll wake you up at dawn, you wash the wax off and leave the hotel before anyone notices."
The man does what he was told.
Early in the morning, the receptionist wakes the customer up. He goes to the bathroom and tries to wash the wax off but nothing happens. Horrified, he scrubs and brushes, there is no more soap left, but no way, he's still black...
... For the receptionist woke up the wrong man.