The TX-32, or the "Twitter" as it became known from the fluttering sounds the engine makes when operational, was a rare Walker design from around 2453. Since Walkers rarely saw military action, this model quickly became feared on the battlefield- while light, conventional light arms couldn't harm the beast.
It became adopted by the Alliance Armed Forces in 2489, during the first Rebellion Years, and then saw action against the Terran Empire ground forces throughout the following years. The design was eventually replaced by the Justice J-MK-53, with modern raigun weaponry and Nightmare anti-personnel missile launchers.
Several smaller human nations still use the Walker, and wealthy pirate factions, including the Gorka Alliance, have also put captured Twitters into service.