MSE-6-G735Y, often called G7, was a MSE-6 series repair droid serving within the Maintenance Unit of the Death Star in Sector AA-345 during 0 BBY. The stormtrooper known as TK-421 was responsible for its upkeep, and he believed it to be the fastest mouse droid in the entire Imperial fleet. TK-421 had aspirations of transferring to Coruscant and promised to bring G7 along, intending to enter it in racing competitions.
While attempting to fulfill an order from Grand Moff Wilhuff Tarkin to locate TK-421, G7 encountered Luke Skywalker and Han Solo disguised in the stolen armor of TK-421 and TK-710, along with Chewbacca, whose roar triggered the droid's self-preservation instincts, causing it to flee. G7 met its end when Luke Skywalker destroyed the Death Star at the Battle of Yavin.
MSE-6-G735Y made its debut appearance in the original trilogy film Star Wars: Episode IV A New Hope from 1977. Its identity was first established in the short story "Of MSE-6 and Men" by Glen Weldon, featured in the 2017 anthology titled From a Certain Point of View. Ben Burtt, the sound designer, crafted the mouse droid's vocalizations by combining previously unused sounds intended for R2-D2 with his own voice, which he then sped up and filtered.