The Orange Station Wagon (closely resembling a 1973 Chevrolet Chevelle station wagon) is Marge Simpson's car, though it has been driven by Homer on occasion, and serves as the family's preferred vehicle when going on vacation due to the larger amount of space.
In one episode, Homer trades his car for a red Canyonero, but then finds out it was designed for women (and gets mocked by Lenny and Carl in the process), so he drives the '73 Wagon (also hotwiring the car so that he wouldn't need to take Marge's keys when she refused to give the keys to him).
In the old opening credits, Marge seems to have a sedan with a star hood ornament. In that same opening, Marge's car is red.
In "Mr. Plow", Homer destroyed both of the family vehicles in a snowstorm, though they show up in the next episode fixed, despite the considerable damage that they sustained. The station wagon was completely damaged, compared to the sedan’s damage on the grille.
The car might be newer than 1973, but it shown to be old enough that it uses a carburetor instead of fuel injection; in Homer the Heretic, Marge and the kids become stranded in the church parking lot when the car won't start due to the cold weather. Lisa advises Marge not to pump the gas pedal too much or else she will flood the engine, which is technique used for starting a carbureted engine.
It was also damaged in "The Heartbroke Kid" when a morbidly-obese Bart collided with the car, his sheer weight sending it spinning away.
In one episode, the car fell into a sinkhole and was buried by a large number of flaming tires. Marge replaced it with a new Tissan Sensible (based on the 1st Gen Nissan Versa), though the wagon was either recovered somehow or another was purchased as it shows up undamaged in the next episode.
At one point, Homer used this car for his grease business, in particular the time he forced Krusty Burger to give him their grease, although he shoveled the grease directly into the back of the car rather than placing it in containers. This caused Bart to tell Homer "Mom's going to kill you!" (implying that Marge would never have approved of Homer using the car as a pickup truck for grease and likely damaging it had she found out), with Homer remarking that she should have done a better job hiding her keys. However, the car's grease proceeded to be sucked out via hose by Acne Grease and Shovel.
Though it seems to be Marge's car, it is possible that Homer owns it or at least bought it for her as when the family went on vacation and some friends of Lisa glued seashells all over it as a tribute to her, Homer exclaimed "Sweet merciful crap! My car!" upon seeing what had been done.
Usually, the license plate is left blank, but when it does have lettering, it varies (see License Plates on The Simpsons). It has appeared to be EP7G08 (EP might mean "Episode" and 7G08 is the production code for the first standalone Simpsons episode, Simpsons Roasting on an Open Fire) on most occasions when it had a license plate.
In many of the standard definition episodes, the station wagon appears red, not just in the opening sequence, but in the episode itself.