A Priest a Rabbi and a Witchdoctor are sitting together on a train.

A fly comes and lands on the priest who waves his arms and shoos it away.
So, the fly lands on the Rabbi who shoos it toward the Witchdoctor.
The Witchdoctor follows it with his eyes for a moment and suddenly reaches out grabs the fly in his fist and eats it.

The other two look on with disgust but say nothing.
When another fly comes near the priest he again shoos it away.
Once again the fly comes to the Rabbi, who with one quick motion reaches into the air, turns to the witchdoctor and says, "Want to buy a fly?"