One day the teacher decides to play an animal game. She holds up a 
picture of a giraffe and asks if anyone knows what it is. No one 
raises his/her hand. The teacher says "See it's long neck? What 
animal has a long neck?"

Sally holds up her hand and asks if it is a giraffe. "Very good 
Sally," the teacher replies. Next she holds up a picture of a zebra. 
None of the students holds up his/her hands. "See the stripes on 
this animal? What animal has stripes?" Billy holds up his hand and 
says it is a zebra. "Very good Billy," the teacher replies. Next 
she holds up a picture of a deer. None of the students recognized 
the animal.

"See the big antlers on this animal. What animal has horns like this?"

Still no one guesses. "Let me give you another hint, it's 
something your mother calls your father."

Johnny shouts out "I know what it is, it's a horny bastard."