A novel electronic system provides real-time movement-mirroring and three-dimensional (3D) holographic avatar superimposition on a human subject or another physical target located in a holographic mixed-reality environment. In the visual perspectives of a holographic mixed-reality environment viewer wearing a mixed-reality headset or another mixed-reality visualization device, the physical target becomes invisible and is replaced by a 3D holographic avatar in the same coordinates of the physical space where the holographic mixed-reality environment is active. Typically, the 3D holographic avatar is chosen by a system user to represent or “body double” a particular physical target prior to activating the holographic mixed-reality environment. Once activated, the novel electronic system provides subject feature extraction, subject-to-avatar recognition, subject pose and expression matching, motion retargeting, and movement mirroring to reflect detailed movements and facial or bodily expressions of the physical target in the 3D holographic avatar in real time.