Urban legends always change as they are passed on from person to person. You start with one set of details, and after the legend has circulated for a while by word of mouth, you find that you've got a somewhat different story.

The process is like that old parlor game usually called "Telephone" or "Gossip." The players stand in a circle, and one person whispers a phrase to the person to his or her left, who whispers it to the next person, and so on. When the last player recited the phrase that he or she heard, it's sometimes barely recognizable as a variation of the original.Perhaps reflecting this process, there are a couple of common legends about objects that are pased around until they return in a new form.

The two items passed on in these stories are a marijuana cigarett and a lottery ticket. It's the pot or the lot, so to speak.

I've collected the legend about the joint from people who remember hearing it as long ago as 1968. These particular people heard it in Alaska, California, North Carolina and Pennsylvania, so I assume that it's known nationwide.

A police officer is giving a lecture about the dangers of drugs to students in a high school. At one point, he puts a real marijuana cigarette on a dish and passes it around for the students to see and smell. "When that dish gets back to me, the cannabis exhibit had better be on it," he warns them. "And if it isn't, there will be an inspection."

When the exhibit comes back to him, not only is the joint still on the dish; there are three others as well.

In some versions, the policeman's threat has been ignored, and the joint has been exchanged for an ordinary cigarette.

I first came across the lottery-ticket variation of this legend in Michigan. The state began to operate a lottery in 1972, and by the end of the year, this story was going around.

A man is in a bar where the lottery numbers are being shown on TV, and he sees that he is a big winner. Thrilled by his good luck, he pases his winning ticket around the bar for everyone to see.

When the ticket comes back to him, though, it's not the same ticket.

A reader from New Orleans tells me that he heard virtually the same story in 1969. The only difference is that a winning horse-racing ticket, not a lottery ticket, is passed around.

That such things do sometimes occur in real life is illustrated by a reader's personal experience described in another letter I received recently.

The reader wrote to tell me about the time she attended the broadcast of a national TV interview program. Among the guests was a celebrity author. Afterward, at a large city bookstore, this reader was able to buy an autographed copy of the author's latest book.

She later told her co-workers about her visit to the show, and several of them asked to borrow the book. She consented, and the book made its way around the office. When it was finally returned to her, after several co-workers had read it, it bore the price sticker of a local bookstore. And the space where the autograph had been was blank.

The lesson of all these stories, I suppose, is that you can't trust people when they are in groups. Whether they are passing around contraband or tickets or books-- or folklore-- someone is bound to pull a switcheroo.