Someone brought a visitor and the new fellow sat fascinated as the funnymen shouted out numbers--"56!" "923!" "307!" Each time a number was called, the others would laugh and laugh.

Finally he asked his host, "What are the numbers for?" The other man explained, "Oh, we've been coming to these conventions for so long, everyone knows all the jokes.  We just categorize them by number and then save time by using the number alone."

ENDING #1: The visitor thought this was an interesting idea, and that he would try it himself.  So the next time there was a pause, he stood up and called out, "468!" The others roared with laughter.  He waited, then called out, "22!" and again everyone roared.  Then he called out, "829!" and there was a dead silence--all except for one guy in the fourth row, who laughed so hard that he fell off his chair and rolled on the floor, seemingly unable to stop.

The visitor poked his host and whispered, "How come he's laughing and the others aren't?"

The host whispered back, "Oh, that's because he never heard that one before."

ENDING #2: The visitor thought this was an interesting idea...so he stood up and called out, "468!" and no one laughed--there was a dead silence.
Puzzled, he turned to his host.  The other man looked away, sniffed, and said condescendingly, "Some people just don't know how to tell a joke."