They shoot horses, don't they? The mechanical ponies that grazed for pennies near grocery-store entrances may well be moving from threatened animals to full-blown endangered-species status. For decades, the brightly colored "equus plasticus" has been sufficiently attractive to compel tots to hop aboard for a slow rocking and their first real taste of sheer boredom. Now, as shopping has become our national obsession, most retailers have found that they need to get kids out of the foyer and into the aisles, where they can badger their parents to make purchases. And so many mechanical penny ponies have been put out to pasture. Just north of downtown, the creatures are corraled, nuzzle to hock, in a chain-link enclosed yard to wait out that awkward time between obsolescence and valuable Antiques Roadshow treasure. Bring a camera: They're just waiting to be shot.