The Japanese are either mocking us or have absolutely no sense of irony to their names.
I mean, when you are stuck behind a car, getting angrier and angrier, what could be worse than the car they are driving advertising that, despite your hatred and frustration, the blue-rinser in the car in front feels "Sunny". They enjoy you being stuck behind them. Because they have a Nissan Sunny.
Of course, it's not just the Japanese. The Czechs have the aptly named Superb, which, in all honesty is an excellent if dull car. It is actually bordering on being Superb, but it's incredibly arrogant to call the car Superb.
The best example of this phenomenon though is from Britain, and is not just the car name but the entire Brand. What would you call a failing car company? Triumph.