In a device-to-device (D2D) local area network (LAN), mobile users (MUs) must cooperate to download common real-time content from a wireless cellular network. However, sustaining such D2D LANs over cellular networks requires the introduction of mechanisms that will incentivize the MUs to cooperate. In this paper, the problem of energy-aware D2D LAN formation over cellular networks is studied. The problem is formulated using a game-theoretic framework in which each MU seeks to minimize its energy consumption while actively participating in the D2D LAN. To account for the selfish behavior of the MUs, a punishment and incentive protocol is proposed in order to ensure cooperation among MUs. Within this protocol, an estimation algorithm is proposed to simulate the process of D2D LAN formation and, then, adjust the mechanism parameters to maintain cooperation. Simulation results show that the proposed framework can improve energy efficiency up to 36% relative to the traditional multicast scenario.