Picture a Saturn 2 sizes smaller than the upcoming Astra and you are well on your way to understanding what the Opel Agila is all about.
This microcar (a niche that GM has becoming increasingly interested in of late - with their 3 microcar concepts shown at the New York Auto Show and talk about their desire to make stylish/desirable products in this segment with the help of GM Daewoo) is based on the Suzuki Swift (yep, they still make a Swift).
It is powered by your choice of 3 tiny engines (a 1.0l gasoline 3-cylinder with 65hp, a 1.2l gasoline 4-cylinder with 86hp, or a 1.3l diesel with 75hp but 140lb*ft of torque). Given this just over 12ft long car's weight, any should be sufficient.
While it is unlikely that Saturn will see this car (since the Opel Corsa is one size bigger and not planned - yet - for the US market) - ever tightening emissions and fuel economy standards, and increasing gas prices may change things in the coming years.
It is nice to know that tiny cars are not the penalty boxes that many remember from the first push to get fuel efficiency up (late 70's-80's).