Next month, Rogue One: A Star Wars Story will take moviegoers back to a familiar time in a galaxy far, far away: when the Galactic Civil War raged between the Rebellion and the Empire. Although the Anthology spinoff will feel different than any other Star Wars movie due to its grittiness and emphasis on the "Wars," there will be plenty of callbacks to the Original Trilogy. Some are major, like Darth Vader returning, while others are more subtle. In the case of K-2SO, the droid voiced by Alan Tudyk, his design was modeled after the visually distinctive probe droid from The Empire Strikes Back.
Because K-2SO was originally an Imperial enforcer droid before he was reprogrammed by the Rebellion, Rogue One executive producer and visual effects supervisor John Knoll informed EW that the production wanted to make him look original, yet still retain some classic elements. To that end, they modeled K-2SO after the Viper-class Imperial probe droid, with a little bit of the IT-O Interrogator from A New Hope (the droid that tortured Princess Leia) mixed in. Knoll said:
It's not the first time we've seen an Imperial droid. There's the Imperial probe droid and the sort of interrogation droid that have these black shells and a kind of sinister, evil-looking character to them.
The Viper-class Imperial probe droid was introduced at the beginning of The Empire Strikes Back. Several were launched from a Star Destroyer, and the one that landed on Hoth eventually the Rebel base. Han Solo tried to destroy it, but after transmitting its coordinates back to the Empire, it self-destructed. Other Viper droids have been seen (canonically) in a few episodes of Star Wars Rebels and the video game Star Wars Battlefront. You can compare its look below to K-2SO's above to see there are any noticeable similarities.
Although K-2SO was created as a weapon to enforce the Empire's will, that won't be his function in Rogue One. Thanks to Cassian Andor's reprogramming, he now serves the Rebellion, making him one of their most valued operatives. Since K-2SO still looks like your everyday Imperial enforcer droid on the outside, he can infiltrate key Imperial installations without anyone batting an eye. Not to worry, though as his allegiance rests solely with with the Alliance to Restore the Republic, and thanks to his continued willingness to drop blunt and pragmatic comments, he'll provide some of the movie's lighter moments. K-2SO will work alongside Cassian, Jyn Erso, Chirrut Îmwe, Baze Malbus and Bodhi Rook in Rogue One to secure the Death Star Plans and bring them back to the Rebellion, though it remains to be seen how their mission will actually turn out.
Rogue One: A Star Wars Story hits theaters on December 16.