(This is a one-hour special) It's the summer solstice and the twentieth anniversary of Phineas and Ferb's greatest feat, a trip around the world in 24 hours. Phineas and Ferb's children long to live up to them, so with their friends, they build the Sun-Beater 4000, and try to beat their parents record. Seizing the oppurtunity, Mr. Biz bets against the kids, if they lose, he takes over Flynn and Co. The grown-ups worry for their childrens' safety and chase them around the world in the Sun-Beater 3000.