"Mason and Ty were once the very best of friends, like two nerdy sides of the same coin--until seventh grade, when Ava Petrakis came along. Now Mason can trace everything bad in his life to that terrible fight they had over the new girl. The one thing he'd give anything for is a do-over ... As a science kid, Mason knows do-overs are impossible, so he can't believe it when he wakes up from a freak accident and finds himself magically transported back...

George and Harold are forced to contemplate a world without Captain Underpants.

When Joe travels back in time to 1944, he meets the Milwaukee Chicks, one of the only all-female professional baseball teams in the history of the game.

From the Jurassic period and the dinosaurs, to a medieval castle, Geronimo Stilton and a few members of his family embark on an adventure through time in Professor von Volt's new time machine, the Mouse Mover 3000.

With their ability to travel through time using vintage baseball cards, Joe and his father have the opportunity to find out whether Babe Ruth really did call his shot when he hit that homerun in the third game of the 1932 World Series against the Chicago Cubs.

Stosh travels back to 1969 to try to prevent the untimely death of Roberto Clemente, a legendary baseball player and humanitarian, but upon his return to the present, he meets his own great-grandson who takes him into the future, and what he finds there is more shocking than anything he has encountered in his travels to the past.

Traveling to 1896 Paris, Geronimo and his friends try to stop the Pirate Cats from stealing the first cinematograph, an invention that ushered in the age of motion pictures.

Substitute middle-school history teacher Rush Revere takes his students back in time to eighteenth-century Boston to experience the start of the American Revolution as it happens.

When Stosh travels back in time to 1941 in hopes of preventing the Japanese attack on Pearl Harbor that brought the United States into World War II, he meets Ted Williams, one of the greatest hitters in baseball history.

Traveling to France during the reign of Louis XIII, Geronimo and his friends enlist in the "mouseketeers" only to discover that the mouse on the throne is an impostor and together they must find the real Louis.