Joke about little johnny

Little Johnny's first grade class was playing "Name That Animal."
The teacher held up a picture of a cat and asked, "What animal is this?"
"A cat!" said Suzy.
"Good job.
Now, what's this animal?"
"A dog!" said Ricky.
"Good. Now what animal is this?" she asked, holding up a picture of a deer.
The class fell silent.
After a couple of minutes, the teacher said, "It's what your mom calls your dad."
"I know!" called out Little Johnny.
"A horny bastard!"