In Pac-Man Championship Edition for the iPhone, one of the achievements is something like "emit sparks for 5 seconds". How do you emit sparks, and what effect does it have?
Sparks happen when you are trying to turn, but can't. That is, when you're pushing into a wall. This also has the side effect of making you turn faster when the turn becomes possible. So if you plan ahead and "spark into" your turns, you'll corner faster than if you had waited until the actual intersection to change your direction.