Raid of the Alien Mice - S1.E24

Haggar sends a group of small robots disguised as rodents to Arus. Almost everybody is ready to blame the chewed electronics-circuitry on Allura's pets before they themselves are attacked and even more of the castle is damaged. The Voltron Force is forced to battle the creatures who have already ruined the defenses, and another robotic Lotor sends in - without being able to ride the elevators to their Lions to fight.