We present the design approach and evaluation of our proto- type called “Ranger”. Ranger is a robotic toy box that aims to motivate young children to tidy up their room. We evalu- ated Ranger in 14 families with 31 children (2-10 years) using the Wizard-of-Oz technique. This case study explores two different robot behaviors (proactive vs. reactive) and their impact on children’s interaction with the robot and the tidy- ing behavior. The analysis of the video recorded scenarios shows that the proactive robot tended to encourage more playful and explorative behavior in children, whereas the reactive robot triggered more tidying behavior. Our find- ings hold implications for the design of interactive robots for children, and may also serve as an example of evaluating an early version of a prototype in a real-world setting.