The MSE-4 was a wheeled labor droid that was made by Rebaxan Columni and used by the Techno Union at its lava mines on the planet Mustafar. A model of the MSE-Series, the droid had been launched by the end of the Clone Wars in 19 BBY, when the Sith Lord Darth Vader terminated the Separatist leadership taking refuge at a mining facility on the planet. A group of MSE-4s scuttered ahead of Vader as he approached his prey, jumping over a gap in the flooring to flee the Sith's presence.
The MSE-4 was a model of labor droid manufactured by Rebaxan Columni as part of their MSE-Series droid line. Owned by members of the Chadra-Fan species, the company invented the MSE droid for use on Chad, the Chadra-Fan homeworld. A local pet of the world named the pleeky formed the basis of the MSE's design, which Rebaxan Columni hoped the galactic market would find cute. Also known as mouse droids, MSEs' usage was only limited by their owners' imagination.
A fifth-degree droid, the MSE-4 was less than 0.3 meters in height and, similar to the MSE-6, had a black box-shaped body with four wheels underneath for mobility. Capable of jumping over gaps in floorings, the mouse droid made squealing noises and was deployed by operators of Mustafar's lava mines to scout for life-support leaks.
Test runs of the MSE-4 and MSE-5 models were launched by Rebaxan Columni before the marketing efforts for and mass-production of the MSE-6, which resulted in the company's bankruptcy toward the end of the Clone Wars between the Galactic Republic and the Separatist Alliance. In 19 BBY, Separatist leaders were accompanied by MSE-4s while sheltering at their mining facility headquarters on Mustafar, a hazardous mining planet ruled by the Techno Union.
To end the Clone Wars, Darth Sidious sent his new Sith apprentice, Darth Vader, to eliminate the Separatist leaders on Mustafar. As Vader walked through a hallway of the Separatist headquarters, five squealing MSE-4s scrambled from the approaching Sith Lord, with each mouse droid jumping over a break in the flooring and dispersing in a disorderly fashion into the facility's control room that housed Vader's quarry. Soon after, Vader sealed the room's exits and proceeded to kill the Separatist inhabitants.
The MSE-4 was based on the mouse droid model featured in A New Hope (pictured).
The MSE-4 appears in the 2005 prequel trilogy film, Star Wars: Episode III Revenge of the Sith, and was identified in the 2006 reference title The New Essential Guide to Droids, written by Daniel Wallace. The scene featuring the MSE-4 was shot on August 25, 2003, at Stage 2 of Fox Studios, Sydney. For the scene, director George Lucas asked Industrial Light & Magic (ILM) on November 18, 2004 to render a model of the mouse droid seen in the 1977 original trilogy film, Star Wars: Episode IV A New Hope. Lucas' intention was to use the quailing droid to imitate rats leaving a sinking ship. Later, Lucas requested ILM's Rob Coleman, Roger Guyett, and John Knoll make the single computer-generated mouse droid they had rendered a quarter of its size, resulting in the creation of the smaller MSE-4 droids.
- The Making of Star Wars Revenge of the Sith
- The New Essential Guide to Droids