CH-33Z was a droid of the MSE-6 series designed for repair tasks. At one point in time, Vosa, a Chadra-Fan, stood on top of the MSE series droid CH-33Z at the Day Star Hotel as she was talking to Faddey, her spy. During the New Republic era, CH-33Z was moving quickly through the corridors of the New Republic Correctional Transport Bothan-5 when Burg, a mercenary from Ranzar Malk's crew, shot and destroyed him while attempting to rescue the prisoner Qin. The destruction of CH-33Z alerted N5 sentry droids to the presence of the crew.
CH-33Z, sometimes called "Cheeze," began as a recurring minor character featured on The Star Wars Show, an online news and variety program. In this show, he would interact with the hosts as the resident sound expert and "mouse droid extraordinaire." His initial appearance was in the show's first episode, which aired on May 11, 2016, but he was not named at that time. The show let fans decide his name through social media. After receiving many funny suggestions, including "Mon Mousema," "Mouse Eisley," "Mouse Windu," and "Mouse Kanata," the show's hosts, Peter Townley and Andi Gutierrez, announced on May 18, 2016, at the end of the second episode, that the mouse droid would be officially called "CH-33Z" or "Cheeze." This name was based on a suggestion by Star Wars fan Colin Bishop (@storydroid) on Twitter.
CH-33Z was brought into Star Wars canon with a short (and fatal) cameo in "Chapter 6: The Prisoner," the sixth episode of The Mandalorian Season One. The episode was directed by Rick Famuyiwa and co-written by Famuyiwa and Christopher Yost, and it was released on December 13, 2019 on Disney+. While his identity was not revealed in the episode itself, the January 2020 episode of The Star Wars Show identified him as CH-33Z. This episode was released on the Star Wars YouTube channel on January 29, 2020. The droid also appeared in "Episode 4" of Star Wars: Jedi Temple Challenge, which was released on the Star Wars Kids YouTube channel on June 24, 2020.