In the TV show "FLEXES ITS MUSCLES," Ms Frizzle takes the bus (and class) to R.U. Humerus' extraordinary Body Shop for repairs -- but Ralphie seizes the opportunity to build a robot to do his chores. The class joins in and they discover how bones, joints and muscles work together to help us move. But they do the job a little too well, and the Ralphiebot starts to take over. Can Ralphie stop the robot before it's too late?