Who was the small man?

It was Christmas, and there was a big party in the house. Guests came and went but the party continued. Then the bell rang. Several people shouted, "Come in!" and a small man opened the front door and came in. Nobody knew him, but the host(主人) went to meet him and took him to the bar for a drink.
    The man sat there happily for an hour and drank. Then suddenly he stopped and looked at his host. "Do you know, "he said, "nobody invited me to this party. I don’t know you, I don’t know your wife, and I don’t know any of your guests. My wife and I wanted to go out in our car, but one of your guests has parked his car in front of our house. So I came here to find him—and my wife is waiting in our car for me to come back."