In later stages of the T-800 infiltrators program, Skynet realized that the endoskeletons lack certain grace of movements which humans poses. The infiltrators looked human (suspiciously well fed, though), but their stiff hips and overall heaviness gave them away. To remedy this problem, Skynet added dance classes to T-800's training routine. As a result, a new series was introduced, with improved motoric functions and a chassis made from lighter alloy, finally capable of elegant motion. Tango proved to be the most efficient dance for proprioception system calibration, hence the series name: Tango-800.