It's Ralphie's turn to take care of Liz, the class pet, for the weekend. But Ralphie left Liz's habitat at school. Children join in the fun as Liz looks for a new home. Scholastic's The Magic School Bus Liz books are beginning science designed for the preschoolers and kindergarteners who are the core audience of the fantastically popular TV show. Liz is the class pet of Ms. Frizzle's class, and like all little children, she's full of curiosity about the world.