In this paper we present an interactive dynamic simulator for humanoid. In our software, the user can interact directly with the robot through a haptic probe and meanwhile feed back with reaction forces subsequent to its actions. The simulator allows also creation and manipulation of virtual objects by the robot, by the human or in a joint collaborative way. This dynamic simulator uses fast computation dynamics and constraint-based methods with friction. It is part of a general framework that is being devised for general prototyping and collaborative scenario studies with haptic feedback. The different ingredients of the simulator are presented with an simulation scenario.