Leap Frog is a company that makes learning toys and 'video games' for little kids. The cartriges play in leapfrog systems (not super expensive) and contain puzzles that are supposed to help you learn. They come in many themes, and have apparently picked up a Sonic X theme here. This is for kindergarden/first grade, and should be available in Target stores in 2007.
The Leapster 2 meant better graphics, bigger games & other upgrades. It also meant a chance to buy the games again, which is what "Expanded play for Leapster 2" edition (at right) for the Sonic X game is about. Interestingly, reviews of this one say that it is both fun and educational. It could be found on Amazon.