When designer Bryan Nesbitt (who now works for GM) designed the PT Cruiser back in 1997, its design was so distinctive and retro that it's now very difficult for Chrysler to upgrade the exterior of the car. Usually a model receives a mid-life refresh, but in the case of the PT Cruiser, that refresh was very mild and most people didn't even notice. The PT Cruiser remained the only car of its type until 2005 when the Chevrolet HHR was introduced.
It too was designed by Nesbitt and it included more interior space and a fresh take on the overall design style. Where does that leave Chrysler? Even they aren't so sure as the PT Cruiser soldiers on for now. Regardless, it still looks great and fresh while providing decent seating and versatility.