R3-S1, nicknamed "Threece," was an R3-series astromech droid part of the Alliance to Restore the Republic. With an overclocked Intellex V processor, R3-S1 picked up a decidedly vain programming flutter. Not assigned to a specific starfighter, she was employed in the upkeep of technology throughout the Alliance to Restore the Republic's headquarters in the Great Temple on Yavin 4. R3-S1 did not work well with others due to her competitiveness, but she excelled at organization, becoming the recognized chief of the astromech droid pool.