Lil Johnny

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 hands are raised, so the teacher says, "See it's long neck? What animal has a long neck like this?"
Sally holds up her hand and says it's a giraffe. "Very good Sally," the teacher replies.
Next, the teacher holds up a picture of a zebra. Again, no hands are raised, so the teacher says, "See the stripes on this animal? What animal has stripes like this?"
Billy holds up his hand and says it's a zebra. "Very good Billy," the teacher replies.
Next, the teacher holds up a picture of a deer. Again, no hands are raised, so the teacher says, "See the big antlers on this animal? What animal has horns like this?"
Still no one guesses.
"Let me give you another hint,"says the teacher. "It's something your mother calls your father."
Little Johnny shouts out, "I know what it is — it's a horny bastard."