Tim Possible and the Time-Travelling T.Rex (Tim Possible #1)

Tim and Tito are best friends whose world gets upended when a time-travelling T-Rex named Oskar suddenly appears in Tim's backyard. That's right, a time-travelling T-Rex, who knows too much for his or Tim and Tito's good. Sure, Oskar's prehistoric spaceship is awesome. But when Tim mistakenly gulps down something called Impossible Juice, the boys find themselves not only battling a loony, robotic lunch lady, but also Oskar's evil AI assistant. Is humanity as they know it on the brink of doom? Or can Tim, Tito and Oskar save the day?