Three different design research topics are presented in this article: how to design social and active play for teenagers, how to design for open-ended 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.