Social media has become an important factor in crisis response. From an improved situational awareness to facilitating communications, it supports responders in more effective crisis handling. Social media also enables affected communities to express their needs and others to respond directly. At the same time social media also poses challenges for responders, handling communications or data overload. To aid professionals in leveraging the potential and overcome challenges, a better understanding of social media as an integrated part of the response operation is needed. While previous research focused on individual aspects or challenges, such as rumor spreading, we use a more holistic approach. Providing a group of volunteers, representing a broad demographic, with various profiles based on real-life cases and actual behavior to act as 'Twitter-simulants'. With these simulants we added a comprehensive, realistic social media component to an extensive crisis exercise. In this paper we present the outline, its design considerations and the initial results, in particular on the achieved realism and added value for responders.