This study explores how Interaction Design could contribute to facilitating imagination and critical thinking in participatory settings. Specifically, it investigates the intersection between Playful Design and Design Critical Practices as a way to support the Re-Imaginatorium, which is an initiative led by Malmö University that aims to facilitate participatory spaces for Critical Imagination. Consequently, the Re-imaginatorium is the main stakeholder and the contextual frame of this study. From the theoretical analysis, the notion of ambiguity was found as a bridging concept between Playful Design and Design Critical Practices for supporting imagination. This was a relevant tool for developing different interactive materials for three Re-Imaginatorium pilots. Different prototypes of materials were created for each pilot. The last one incorporated multisensorial elements, including visual, sound, smell, and tactile resources. This last one demonstrated that the concept of ambiguity combined with interactive and multisensorial resources, enables a playful attitude, that in turn could potentially contribute to critical and collaborative imagination. Feedback from each test was incorporated into a concept of a ToolKit for the Re-imaginatorium.