The MSE-6 series repair droid, often called a mouse droid, was a mobile repair droid that was widely used – often in great numbers – to maintain the cleanliness of starship floors and base interiors. In addition to cleaning, they also functioned as message carriers and guides, leading troops to their designated locations. These compact, box-shaped droids navigated on four partially concealed drive wheels. A compartment on top of the droid held sealed instructions. Although they were relatively basic compared to more sophisticated, autonomous droids, MSE-6s could still handle a range of complex operations.
Rebaxan Columni designed the MSE-6 during the era of the Galactic Republic, and it remained a common fixture on starships for many years. The Galactic Empire, which succeeded the Republic, continued to use the MSE-6, as did the subsequent governments of the New Republic and the First Order. The Confederacy of Independent Systems also utilized the MSE-6, along with the criminal syndicate known as the Haddrex Gang. The droid's widespread presence led to a thriving market for modified mouse droids, which were adapted for purposes such as surveillance and data slicing.
The MSE-6 series droid was created by Rebaxan Columni during the time of the Galactic Republic. As a member of the MSE series of maintenance droids, and resembling a scaled-down version of a larger droid with similar design principles, the MSE-6 was primarily used for shipboard repairs. Typically, numerous units were deployed simultaneously. The MSE-6 had a height of 0.25 meters and featured black exterior panels. The internal components of an MSE-6 included various wires, indicator lights, and buttons. This internal interface allowed for the droid's reprogramming.
The MSE-6 was outfitted with both a data probe and a grasping claw. Furthermore, it included a command order tray designed to hold sealed instructions.
Despite its relative simplicity when compared to other droids, the MSE-6 series repair droid was capable of performing a variety of complex functions. These included cleaning floors, delivering messages, and directing troops to their assigned locations. In one unusual instance, an MSE-6 droid was used for the disposal of deceased individuals.
The droid's inconspicuous nature contributed to a growing secondary market for modified MSE-6 droids, repurposed for espionage and data breaching.
MSE-6 series repair droids were prone to being easily startled, as demonstrated by the example of MSE-6-G735Y. Mouse droids also exhibited a degree of wariness towards people, as seen when Tamara Ryvora attempted to entice 5-L for reprogramming, or when Burg attempted to lure a mouse droid stationed on a New Republic prison ship in order to shoot it.
A particular MSE-6 droid was present in a residence located in Mos Espa on the desert world of Tatooine. In 28 BBY, Sabé, a Naboo Royal Handmaiden, resided in this house for a period of six weeks while engaged in efforts to liberate slaves on the planet. During her stay, she attempted to ignore the droid, but her companion Tonra developed an affinity for it over the course of their mission. Upon being recalled to Coruscant by their leader, Senator Padmé Amidala, he suggested to Sabé that they bring the droid with them. The mouse droid experienced difficulty with its mobility, often spinning in circles due to its wheels.
During the Clone Wars, at least one MSE-6 droid was stationed within the Citadel on Lola Sayu in 20 BBY. It was present when several Jedi and clone troopers attempted to rescue Even Piell from the prison facility.
One MSE-6 droid was a member of the crew aboard a Venator-class Star Destroyer controlled by Separatists, having been seized by the Separatist Droid Army. This mouse droid survived the takeover along with other droids, while all clone personnel on board were eliminated. When D-Squad boarded the Venator, they encountered BNI-393, who led them back to their shuttle where the surviving droids, including the MSE-6, were hidden. The group then followed a buzz droid through the ship. After the buzz droids were neutralized, the group returned to the shuttle and escaped before the Star Destroyer detonated before it could reach its target, the Republic space station Valor.
Near the conclusion of the Clone Wars, several MSE-6 droids were present at a Techno Union installation on Mustafar. When Darth Vader arrived to eliminate Separatist leaders, he startled several mouse droids, causing them to scatter out of his path.
During the era of the Galactic Empire, specifically in or before 14 BBY, Darth Vader commanded a Venator-class Star Destroyer which served as his flagship. An MSE-6 droid was stationed on board. On one occasion, Darth Vader instructed this MSE-6 unit to prepare his meditation chamber. However, the droid was interrupted by Admiral Mummert, who informed Vader that he could not deploy starships to the Hortolo system by the set deadline. In response, Vader used the Force to strangle Mummert to death due to his excuses.
Following this, an Imperial general arrived and informed Vader that only 10,000 of the required 50,000 troops were ready for deployment to the Winnikk system. Vader, again using the Force, choked him to death as well. Vader then commanded the MSE-6 unit to dispose of the body. After completing this task, the MSE-6 unit resumed preparing the chamber.
Subsequently, another officer appeared and informed Vader that they were unable to repair Vader's ship. Vader, expressing his dissatisfaction with their efforts, choked him to death as well. Vader then ordered the MSE-6 to drag away that officer's body as well. Finally free from interruptions, Vader remarked to the MSE-6 that it was the only one who had not provoked his anger. The droid then inadvertently bumped into Vader, leading Vader to destroy the MSE-6 unit.
During the Galactic Civil War between the Alliance to Restore the Republic and the Galactic Empire, Imperial Agent Alexsandr Kallus, who secretly operated as Fulcrum, a Rebel spy, utilized a reprogrammed MSE-6 droid to eavesdrop on a conversation between Grand Admiral Thrawn, Governor Arihnda Pryce, and Admiral Kassius Konstantine.
Throughout the Imperial Era, MSE-6 droids were commonly used aboard Imperial starships. In 0 BBY, the mouse droid MSE-6-G735Y, known as G7, was stationed on the DS-1 Death Star Mobile Battle Station. G7 was recognized as the fastest mouse droid within the Imperial fleet, to the extent that TK-421, the stormtrooper responsible for its maintenance, desired a transfer to Coruscant with the droid to enter it in racing competitions. It collided with Chewbacca when he, Han Solo, and Luke Skywalker were captured by the Death Star's tractor beam. Chewbacca roared at G7, causing it to flee in fear. It was functioning as a messenger between TK-421 and the Imperial officer he was in love with.
The MSE-6 unit Petyr was a crusader within the Second Revelation droid movement, operating undercover within the Empire to locate other enlightened, sentient droids. Its sacrifice enabled the Second Revelation to address the threat posed by the Scourge, which utilized MSE-6 units as carriers for infective spider-droids to propagate its consciousness to other droids throughout the galaxy. The Tagge Corporation employed MSE-6s during the period of the Scourge, with certain units displaying the company's golden emblem on their front.
During the era of the New Republic, at least one MSE-6 droid was stationed on the New Republic Correctional Transport Bothan-5 in 9 ABY. This mouse droid, named CH-33Z, was present when the Mandalorian Din Djarin, the human Migs Mayfeld, the Twi'lek Xi'an, the Devaronian Burg, and the droid Q9-0 conspired to break Xi'an's brother, Qin, out of the vessel. Upon boarding, the group encountered the droid. Burg then shot and destroyed CH-33Z, much to the dismay of his comrades, which alerted security droids to their presence.
Several MSE-6 units served Moff Gideon at the hidden Imperial base on Mandalore during the New Republic Era. They were present when the Children of the Watch and the Mandalorian resistance launched an attack on the base. During the assault, it encountered R5-D4 slicing into the base's computer to disable ray shields and confronted the astromech, before being shocked and forced to retreat. Later, the droid returned with several other mouse droids to again confront the interloper, only for it to fly away, causing one of the mouse droid to fall off the ledge. All the mouse droids were equipped with lightbars and sirens.
Komat, a former member of the Acolytes of the Beyond, possessed a mouse droid named M-1 while living in exile on the planet Polaar. She used M-1 as a danger signal due to the planet's distronic radiation poisoning.
During the conflict between the First Order and the Resistance, a mouse droid named 5-L was stationed aboard a Resurgent-class Star Destroyer. When Tamara Ryvora, a TIE pilot, decided to defect from the First Order, she reprogrammed 5-L to assist her. The Resistance also utilized MSE-6 Droids aboard the MC85 Star Cruiser. Around this time, Kat Saka's Kettle food stand in Black Spire Outpost sold their popped grain items in souvenir containers crafted from hollowed-out MSE-6s.
MSE-6 series repair droids made their debut appearance in the 1977 film Star Wars: Episode IV A New Hope. Their formal identification occurred in the 2015 reference book Star Wars: Absolutely Everything You Need to Know, authored by Adam Bray, Kerrie Dougherty, Cole Horton, and Michael Kogge. During the production of the original Star Wars film, the droid underwent testing by production designers on March 15, 1976, where it was initially referred to as "baby box." The droid's test run was filmed by cameraman Gilbert Taylor and directed by George Lucas.
While both Absolutely Everything You Need to Know and the Mouse Droid entry in the StarWars.com Databank specified the height of MSE-6 series repair droids as 0.25 meters, the 2020 reference book Star Wars: Extraordinary Droids indicated a height of 0.4 meters.