Who goes to heaven - a good joke

A man dies and goes to heaven. At the gates he meets St. Peter who welcomes him and shows him inside. "This is beautiful!" the man says as he is shown around the pool, the golf course, the night clubs, the hiking mountains and camping forests, the cruise ship, the zoo and menagerie, everything everyone could ever want or like. St. Peter introduces the man to God. "You're exactly what I thought you'd be like!" the man said. "Everyone says that," smiled God. God began to introduce the man to all the people in heaven. "This is my son Jesus," he said and the man nodded. "And my son Muhammed," and the man blinked. "And my son Buddha, my daughter Brigid..." God went on and the man stopped him for a moment. "I thought you had only one child." God smiled. "You are all my children. Now, over here are the Catholics," God continued pointing out peoples. "And the Buddhists, and the Jews, and the Pagans, and..."
"God, wait... you didn't say what's through this locked door."
"Oh, shh," God hushed the man and gestured him to come on. "Those are the people who think they're the only ones here."