When researching interactive systems in the car, the design space can be divided into the following areas: driver, front seat passenger and rear seat. The latter has so far not been sufficiently addressed in HCI research, which results in an absence of implications for interaction designs in that space. This work presents a cultural probing study investigating the activities and the technology usage in the rear seat as social and physical space. The study was conducted with 20 families over a period of four weeks and unveiled aspects relevant for HCI research: aspects of diversion, educational motivation, togetherness, food as activity, physical space, perception of safety, and mobile computing. In relation to these areas, implications for the design and integration of interactive technology in the rear seat area are deduced. We show that cultural probing in the car is a promising and fruitful approach to get insights on passenger behavior and requirements for interactive systems. To improve the rear seat area and to show the potential of probing results to inform design, a design proposal for an interactive rear seat game called RiddleRide is introduced.