IT’S not the old toy tin car or the plastic model assembled with glue. This toy, the Playsam Streamliner, is a five-inch painted wooden car that has become as powerful a symbol of Swedish design as a Volvo or an Ant chair.

The design of the Streamliner is basic, a geometric nursery rhyme of a body and wheels and nothing more. It has been designated an official Swedish design classic by the Swedish National Museum and Swedish Design Council. Now, the Fitzsu Society, a shop in Los Angeles dedicated to modernist tabletop accessories and other items for the home, has persuaded artists and designers to create variations on the Streamliner. These have been auctioned to support a charity, the World Children’s Foundation.

For his contribution, Michael Graves mashed up the car with his familiar teapot. Scott Henderson put a driver inside his version. The October auction, called FitzsuGrandPrix, raised about $20,000.

Playsam was founded by Carl Zedig, and the original Streamliner was designed in 1984 by Ulf Hanses.

The secret to the Streamliner, Mr. Zedig has said, is that it is so simple everyone mentally adds their own details.

Playsam has a rival, of sorts, in Automoblox of Roseland, N.J. Its cars are nearly as spare and basic as the Streamliner. But unlike the Streamliner, wheels, tires, tops and bottoms can all be interchanged.

The Automoblox cars cost about $35, the same as the Streamliner.