AP-5 is a former Republic analyst and navigation droid reduced to Imperial cargo inventory work, introduced in the Star Wars Rebels episode "The Forgotten Droid" (2016) and voiced by Stephen Stanton. He defects to the Rebellion after an unlikely friendship with Chopper, and it is his navigational data that finds the fleet a base.
Stanton plays him as a magnificently depressed English butler, which is the joke: the most lugubrious voice in the series belongs to a droid whose job is counting crates. He is the only character in Rebels that Chopper treats with anything resembling respect, and the two of them bickering is reliably the best thing in any episode they share.
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