M-TD, an abbreviation for "miniaturized translator droid," also known as Em Teedee, functioned as a specialized translation unit for Lowbacca during his time at Luke Skywalker's Jedi Praxeum. Given that "Lowie," like most Wookiees, lacked the physical ability to speak Galactic Basic, M-TD was programmed to convert his native Shyriiwook into a language understandable by his companions.
Chewbacca, Lowbacca's uncle, constructed the droid, and C-3PO handled the programming after Chewbacca became aware of his nephew's plans to attend the Jedi Academy.
When the young Wookiee arrived at the Jedi Praxeum, Chewbacca presented Lowbacca with M-TD. Anyone who had interacted with C-3PO for any length of time could not help but notice the striking similarities between M-TD's personality and that of his programmer. M-TD's habit of embellishing Lowbacca's statements in his translations proved to be a constant source of irritation for Lowbacca and his friends. He justified his actions by claiming that his translations were more polished and would make Lowbacca seem more cultured.
Lowbacca, in turn, frequently caused M-TD considerable distress by failing to properly secure the small droid to his syren fiber belt, resulting in accidental falls. On one of the initial instances, the young Wookiee was racing through the Yavin 4's jungle, attempting to alert the Praxeum to the kidnapping of Jacen and Jaina by Qorl, a TIE fighter pilot who had been residing in the jungle since the Battle of Yavin. M-TD experienced a gentle landing without hitting the ground, but he was then captured by a woolamander as a prize. Fortunately for M-TD, Tenel Ka, who had lost her way, discovered him and utilized his navigational skills to find her way back to the Praxeum, ultimately returning him to his owner.
During the raid on GemDiver Station, the Shadow Academy abducted M-TD, along with Lowbacca and the Solo twins. He was immediately separated from Lowbacca, leading to significant confusion between the young Wookiee and his Human companions. After Lowbacca succumbed to his anger and destroyed a sonic generator, M-TD was returned to him as a reward by Tamith Kai.
However, M-TD had undeniably changed: he had become uncharacteristically disobedient toward Lowbacca, scolding him whenever he violated the Shadow Academy's rules. Most alarmingly, he began uttering phrases such as "The Empire is your friend" and other pro-Imperial propaganda. As he eagerly informed Lowbacca, Brakiss and Tamith Kai had reprogrammed M-TD to serve as an "integral part" of Lowbacca's education at the Shadow Academy.
Despite this, due to threats from Jacen, Jaina, and Lowbacca, M-TD assisted them in escaping their confinement. Although he cautioned the trio that he felt obligated to sound an alarm, his programming did not prevent him from infiltrating the Shadow Academy's computers to acquire passwords that would lock all of the Shadow Academy's doors and disable its cloaking device. This action was quickly followed by an alarm. Upon their eventual rescue, M-TD's original programming was restored, and he reverted to his former annoying self, but he harbored "exceeding vexation" toward Brakiss and Tamith Kai for compelling him to violate his core programming.
Subsequently, M-TD accompanied Lowbacca and his friends on their vacation to Coruscant. Upon arriving on the planet, he was overjoyed to discover that his programmer, C-3PO, was there to greet them. The two droids exchanged accounts of the harrowing experiences they had endured since their last encounter.
Lowbacca's vacation, and consequently M-TD's, was abruptly cut short when it was discovered that the cloaked Shadow Academy was orbiting Coruscant, abducting Coruscanti youths and disrupting the flow of traffic in and out of Coruscant.
M-TD joined Lowbacca on the mission to Myrkr in 27 ABY. Lowbacca detached M-TD and left him on board the Tachyon Flier. He was on the ship with a barely conscious Raynar Thul when the Dark Jedi Lomi Plo and Welk hijacked it. The last communication the strike team received from him was his complaint about being stolen. M-TD was destroyed when the Tachyon Flier crashed on the planet Yoggoy in the Unknown Regions. Jacen Solo discovered his remains in 35 ABY, although he could hardly recognize the small droid, which had been melted and fused to the floor.
After being programmed, M-TD possessed the ability to communicate in six different languages and specialized in Human-Wookiee communication. M-TD's yellow photoreceptors were capable of providing illumination to compensate for varying light levels. He was also equipped with olfactory, directional, and auditory sensors. Given that Lowbacca would be spending a considerable amount of time on Yavin 4, Chewbacca also loaded a limited database of the jungle moon's geography and wildlife into M-TD's memory banks.
When M-TD accompanied Jacen, Jaina, Tenel Ka, and Raynar Thul on a mission to the factory world of Mechis III, a system of Micro repulsorlifts was installed on him. Additionally, his language database was expanded by ten, increasing the total number of languages that M-TD could translate to sixteen.
In contrast, C-3PO has the ability to speak over six million languages.
Throughout the Young Jedi Knights series, where he made his debut, his name was consistently spelled "Em Teedee." The "M-TD" spelling was later introduced into canon.
The appearance of an M-TD unit on Coruscant immediately following the Clone Wars in Republic 80 should be considered an anachronistic continuity error.