Along with a nickel cigar and a 25-cent gallon of gas, you can chalk up another vanishing species: sitting through a movie twice on one ticket.

Movie theaters certainly have the right to clear the house after each showing if there's another houseful waiting to get in. But many theaters clear people out when there's no throng outside. They'll even clear out customers who arrived late for Showing A and only want to stay through the first part of Showing B to catch up on what they missed.

So it went one night at the White Flint 5 movie theater in White Flint Mall. As Melissa Bell of Potomac watched and listened, an elderly couple started arguing with an usher about whether they could stay for the beginning of the next showing.

The couple explained in halting English that they had missed the beginning of Showing A and wanted to stay for the first few minutes of Showing B so they'd get their money's worth.

The usher refused several times; the couple insisted several times. Finally, in a masterstroke of bad judgment, the usher called the police, who arrested the couple for disorderly conduct. Meanwhile, all of two dozen people were waiting to get into Showing B.

Lindsay Hurst, manager of the theater, agreed that it was "pretty bad to have called the police on a couple of old people." He said it shouldn't have happened, and won't happen again. He also said that the Can't-Stay-For-Showing-B policy applies only on weekends, because "it's only on the weekends that we sell out." However, Lindsay added that the policy is not suspended for weekend shows that obviously aren't about to sell out.

Well, that's one change that ought to be made immediately. Another is to show elderly people a little consideration. Does it really make sense to tag an elderly couple with arrest records simply because a 20-year-old usher got frustrated? File this one under: People Who Think They're Getting Away with Something, But Who Are Really Costing Themselves Money In The Long Run.

A woman called the other day to say that she "could see them doing it right this minute." "Doing what?" I inquired. "Dumping trash," she said.

The woman lives in an apartment that overlooks the rear of a shopping center in Oakton. She said that all day, every day, she watches people who have no connection to the shopping center or any of its stores drive up to the dumpsters in the alley and throw trash in them.

Of course, the woman often shops at the Oakton center, where she has learned that the individual businesses pay the cost of trash removal. Which means that extra trash costs each business extra bucks. Which means that the cost is inevitably passed through to customers just like my caller.

Who's doing the extra dumping? Mostly construction workers and tradesmen, my observer says. But a spokesman for the company that manages the center says the sinners are anybody and everybody.

"You should see these people in their Cadillacs and Mercedes using the dumpsters, especially on moving day," said the spokesman. "They get pretty upset when they're told not to use them."

How bad does it get? The Oakton spokesman remembered an episode a few years ago in which one of his tenants noticed "four things" sticking straight up in the air out of his dumpster. He dug around and discovered that someone had dumped a dead pony. The "four things" were its legs.

The Oakton center is much more prone to illegal dumping than bigger shopping centers, because its dumpsters are exposed, and easily accessible.

"We do not have a problem here. We have four compactors, and they're not really in public view," said Stanley Jaffe, general manager at White Flint. "Ours are in our truck tunnel, so that's not a problem here," said Chuck Cope, GM at Tysons Corner. "We're kind of out of sight. It's not a problem," added Bunny Austin, associate marketing director at Montgomery Mall.

What's the answer for the Oaktons of this world -- and for their neighbors who notice illegal dumping? Call the police. There are antidumping laws on the books in every jurisdiction. But they won't help us unless we use them. Benjamin and Brendan Moyer live in Gaithersburg, but twice a week they ride to the Washington Cathedral, where they serve as choir boys.

It's not the most scintillating ride in the world when you do it as often as the Moyers do. So they decided to liven things up with The 50 State Game.

They kept track of the license plates they spotted to see how long it would take them to notice at least one plate from each of the 50 states.

The answer turned out to be six weeks. The Moyers began on Oct. 1. They finished with Idaho on Nov. 15. Besides the Magic 50, the Moyers also saw plates from Canada, France, Germany, the U.S. Government, the District of Columbia and those red-white-and-blue DPL tags.

The Moyers would like to challenge my readers to beat their record. Happy hunting, plate-viewers. Frank J. Nivert of Falls Church says he has discovered that inanity and insanity are closely related. To get from the former to the latter, says Frank, all you have to do is make an S of yourself. This Sunday, more than 100 Washington artists will cooperate to help an outfit that is doing excellent, necessary work -- and that needs money.

The artists will hold a benefit art sale. All works will be priced at $100. All proceeds will go to the Whitman-Walker Clinic in Adams-Morgan, where many of the area's AIDS victims are being treated.

The sale will be held at Gallery K, 2032 P St. NW, from noon to 6 p.m. Further information: Jody Mussoff or Komei Wachi at 223-6955. This one froze me in my tracks for days. But the other day, in midshower, I suddenly unfroze.

Susan Lothrop started things off by writing that she had seen the following license plate:

KEMO BE.

The only clue Susan offered was that the car that bore the plate was a Saab. Still . . . .

And then it dawned. Remember what Tonto used to call The Lone Ranger? If you don't, just put the word "Saab" between the "Kemo" and the "Be." CHILDREN'S HOSPITAL

Thank you, Anne F. Neville, for sharing a wonderful memory -- and a historic document.

Anne writes that her sister, Emily, was saved by Children's back in 1934. More exactly, Anne says the saving was done "by a dedicated staff and non-money-hungry doctors."

As soon as her sister was released, the family received a postcard from the hospital. It asked the family to give a dollar a day to provide "food, nursing and medicine . . .for a sick child."

Anne has saved the card all these years, and of course she gets a giggle out of it now, since keeping a child going at Children's would cost a lot more than a buck in 1985.

But there is still a dedicated staff there, and there is still an army of non-money-hungry doctors. There are also more than 200 patients, many of whose families can't afford the medical care their kids are receiving.

We mid-80s types don't have to sign Anne's card. All we have to do is the following:

TO CONTRIBUTE TO THE CAMPAIGN:

Make a check or money order payable to Children's Hospital and mail it to Bob Levey, The Washington Post, Washington, D.C., 20071.