A woman who lived next door to a preacher was puzzled by his personality change in the pulpit.

At home he was shy, quiet and retiring but in the church he was a real fire and brimstone orator, rousing the masses in the name of God. It was as if he was two different people.
One day she asked him about the dramatic transformation that came over him when he preached.
"Ah," he said, "that's my altar ego."