In Rogue One: A Star Wars Story, the reprogrammed Imperial security droid who joins the rebels is K-2SO.
K-2SO is an Imperial KX-series security droid captured and reprogrammed by the Rebel intelligence officer Cassian Andor. After his programming is altered, he works with Andor and becomes part of the team sent to obtain the plans for the Death Star. His immense height, blunt speech, and dry humor make him one of the film’s most recognizable characters.
Alan Tudyk performed and voiced K-2SO. The character was created specifically for Rogue One, the 2016 standalone Star Wars film directed by Gareth Edwards. Unlike protocol droids such as C-3PO, K-2SO is designed for security and combat operations.
The designation uses the numeral 2 followed by the letter S and the letter O. It is often mistyped as K-2S0, replacing the final letter O with a zero. K-2SO’s sacrifice during the assault on Scarif is part of the film’s conclusion.