A little koala bear wanders into a whorehouse. He climbs the stairs and finds a door open. He goes in to the room to find a naked prostitute asleep on the bed. He quickly climbs into the bed and begins performing oral sex on the prostitute. She wakes up and decides that since it feels so good she'll let him finish.
The koala finishes, wipes his chin, climbs off the bed and heads for the door. The prostitute jumps up and yells at him "Hey, you have to pay for that". The koala shrugs and continues to head for the door. The prostitute yells at him again, "Hey you have to pay for that. I'm a prostitute".
She gets up and pulls a dictionary off a shelf and shows the koala the definition.
PROSTITUTE (n) a person receiving payment for sexual services.
The koala shrugs, takes the dictionary and turns the pages to the it definition of koala bear.
KOALA (n.) a small bear that eats bushes and leaves