Their origin is unknown, but the undeniable fact is that they are highly intelligent and seem to understand Human speech. Despite their small size and mischievous nature, they have proven to be worthy allies on countless occasions. The two adult mice are called Platt (the male large blue) and ChuChule (the female pink). Their children are never named. When Fala was a child, the mice befriended and entertained the lonely Princess. She has said that they were her only friends growing up, as thoughts of her family, executed by Emperor Daibazaal, overwhelmed her.
As the series begins, Suzuishi first spots the mice as the team approaches the ruins of Castle Gradam. Not long after, the mice are revealed to have the precious Black Lion Key, which they give up at Fala's request, enabling the team to form Go Lion for the first time. When Sorceress Honerva infiltrated the castle disguised as Fala's long-lost aunt, her aversion to the Space Mice very nearly gave her away, and caused her to set her cat familiar Jaga against them. The Space Mice and the Blue Cat became quick archenemies. On one occasion when Raible and Hys were holding Fala under virtual house arrest to prevent her from flying Blue Lion, the mice bit through her bonds and freed her. When Galra sent alien rats to attack the castle's defense computer, the Space Mice bravely turn the intruders' back, this despite being blamed at first for their damage. On another occasion, one of the Mice hid in Fala's uniform, only to regret it, since she was visiting an ice planet. On one more mission, the Mice's tagging along put them in position to rescue the team from being executed by Sincline. Most often, the mice could be found avoiding execution themselves at the hands of Hys, who saw them as filthy little thieves, and Suzuishi, who wanted to train them to dance for a galactic road show.
The little family's proudest moments came when Seido and Suzuishi constructed them their own Mouse-shaped Mecha/Ship, which they flew into battle against Jaga, who was spying for Honerva, and even aiding the team in finding and destroying a hidden MechaBeastman. Platt and ChuChule had a comical falling-out over Platt's gung-ho training, but it seemed to have paid off. The mice used their little ship to aid in the invasion of Galra itself. When the Beastman made in the image of and controlled by Emperor Daibazaal had Go Lion on the ropes, the mice aided in helping the team restore their battle sword, which Daibazaal had broken, resulting in his death. Finally, when the team stood helpless as Shirogane Ryou was held hostage by Sincline, a shot from the Mouse Mecha distracted Sincline long enough for Ryou to kill Sincline, and sadly himself as well. The last seen of the mice was when Raible (who now seemed to understand them) asked where the Go Lion team was, since they were missing a celebration in their honor. Platt, Chuchule and the children made a motion of someone taking a nap, since the team was doing just that. All four major villains learned the hard way not to dismiss these lovable little rodents.
Except for inconsistent names, the Space Mice are almost exactly the same in Voltron.