Seen in The Empire Strikes Back
While on a routine patrol, Han and Chewie investigate the source of a strange signal, and discover an Imperial probe droid, which immediately fires upon the pair. When Han returns fire, the droid self-destructs – but not before it tells the Empire where the Rebel's base is located. As the Alliance begins an immediate evacuation of Echo Base, R2-M5 [sic] helps coordinate plans and K-3PO provides tactical support to hold back the Imperial forces.
