The 2010 Toyota Prius
We can thank Wunibald Kamm (1893 – 1966), for the flat-backed teardrop design of both vehicles. Kamm was a German engineer who pioneered the science of auto aerodynamics; he discovered that while a teardrop shape was the most efficient way for an auto to cut through the air, lopping off the back didn't change the dynamics—and it made for a more practical consumer car design.
The 2010 Honda Insight
Considering the irrefutable science behind Kamm's discovery, get used to the idea that any future automobile designed purely (or primarily) for gas efficiency will have this same shape. Of course, plenty of hybrid cars built today don't employ the truncated teardrop design, which means a gas-wasting compromise has been made to consumer design tastes. Consider also that Kamm made his energy-saving discovery in the late 1930s, when most cars were boxy, SUV-sized, and inefficient. (Insert your rueful cliché of choice here.)
Top image via