Leo the Lizard and Squirtle the Turtle live in the classroom terrarium of an elementary school. They have been observing the students' growth for decades, and they have a good understanding of children's psychology. They can even speak, but they keep it a secret from humans. One day, Leo hears that his species of lizard can live up to 75 years, and when he calculates that he is already 74 years old, he realizes that his life has passed him by and that he has not seen much of the world. At this time, a substitute teacher decides to teach the students about responsibility and assigns them to take the class's pets home for the weekend....