Answer: The back of his head.
or
Two — one to change the bulb, and one to write a song about how good the old light bulb was.
or
2 years old.
Cow: "Mooooove over"
Sheep: "Naaaaaaa."
or
The bartender offers him a warm smile and says, "For you, no charge".
or
Punch.
or
When the spider spied her!
or