This research explored ways of utilizing social media to engage passive citizens in public policy development using a design intervention. The intervention was designed to enable the users to derive policy needs from their daily life contents. We implemented the intervention in Facebook by posting stimuli on a Facebook page and collecting user comments. A qualitative comment analysis shows that the users' playful grumbles on daily life could evolve into collective needs on public policies through the intervention. We also identified social media functions that facilitated the intervention. Based on the findings, we discussed how social media systems could be developed to engage passive citizens for bottom-up public policy development.