[I poached this straight from the Political Forum, of all places!]

A koala bear was approached by a prostitute. Since he had never been with one before, he was curious and excited. They spent the night together in a hotel, and he had sex with her again the next morning, one last time before departing. As he was heading for the door, the prostitute yelled, "Hey, what about my money?"
The koala turned, gave her a puzzled look and shrugged his shoulders. She said, "Come here," and pulled a dictionary out of her purse. She pointed to the word "prostitute" and its definition, "Has sex and gets paid."
Finally understanding, the koala borrowed her dictionary, turned to the word "koala" and showed her, "Eats bush and leaves."