Three different design research topics are presented in this article: how to design social and active play for teenagers, how to design for openended and emergent play, and how to evaluate interactive playful installations in situ. The Wiggle the Eye installation, five interactive wiggle benches and a central lamp, was iteratively developed and evaluated with more than 1000 users, at two high schools, one university and a design festival. The installation succeeded in inviting teenagers to play in a social way, yet the interaction design proved challenging: uncoordinated mass usage and a variety of external factors influenced the exploration and discovery process for the users. The presented insights serve as advice for everyone designing for teenagers, public spaces or playful interactions.