This is book number 10 in the Geronimo Stilton Graphic Novels series.
Athens, Greece: the first Olympic Games are about to take place, and the Pirate Cats have traveled back in time to enter the competition. The fiendish felines plan to win as many events as they can, and become legendary athletes. But these cats aren't exactly in playing shape! In order to gain an edge, they bring all sorts of modern-age sports gear to improve their odds of winning. It's up to Geronimo and the gang to foil their scheme and save history.