MSE-series

MSE-series was a popular line of MSE "Mouse" droids. These droids were usually programmed with a single function that varied per assignment. Once they were set on the task, they would do nothing else.

History
The MSE-Series General-Purpose Droid was originally sold to the Chadra-Fan homeworld. They mimicked the pleeky, a common household pet. They thought that the Galactic market would consider it "cute", and manufactured these droids in the billions. They sold very well but most of them were returned, as they reminded people of disease-carrying vermin. In one event, the entire Aar'aa species sent them back. The reason was that the little droids skittering underfoot made them uncomfortably hungry. Eventually they became so desperate that they offered every one of the droids to the Imperial Navy, as they were short on droids and needed to catch up with the other Imperial forces. They offered them for a small price and gave all of them to the Galactic Empire; every ship in the fleet had hundreds of them. Their use was only limited by their owner's creativity. These droids were often used to carry messages in vast Imperial ships and battle stations as well as leading troops through mazes of corridors to their assigned posts. They also had two small internal arms and they could do a variety of tasks such as sanitation and security. On the Death Star, they led stormtroopers through its many hallways and levels. They were programmed to melt their processors upon capture, creating a small, localized explosion. In the Yuuzhan Vong War, some MSEs were updated to serve as miniature YVH 1 droids that specialized in detecting ooglith masquers.

The droid factories in Uffel produced a successful variant of the MSE-series, the MSF-series, at some point between 90 BBY and 53 BBY.

A mouse droid was also seen opening the door to Tyber Zann's cell on Kessel and showing a hologram of Jabba the Hutt.

Behind the scenes
The mouse droid has found its way into the Hasbro toy line three times now. The 1999 fan exclusive Power of the Force 2 Freeze Frame Death Star Droid came packaged with a model mouse droid. The 2002 Power of the Jedi astromech droid R4-M9 also came packaged with the same mouse droid model. The droid was released a third time as part of the 2011 San Diego Comic Con Exclusive "Revenge of the Jedi" Death Star set. This model was of a single piece hollow plastic mold construction with non movable wheels.

In Robot Chicken: Star Wars Episode II, the droid is piloted by a real mouse.

Non-canonical appearances

 * LEGO Star Wars III: The Clone Wars
 * LEGO Star Wars II: The Original Trilogy
 * LEGO Star Wars: The Complete Saga
 * Tag & Bink Are Dead
 * Star Wars: Tiny Death Star