E-3PO units represented a specialized offshoot of the 3PO-series protocol droid line. These droids were crafted for usage by the Imperial forces and were equipped with the proprietary TechSpan I module. This module enabled them to connect to the diverse network systems used by the Galactic Empire. Due to their limited production and relative obscurity, E-3PO units often developed a sense of superiority, arrogance, and haughtiness, earning them a certain degree of infamy throughout the galaxy.
During the period of the Galactic Civil War, the production facilities for E-3PO units, located on Mechis III, were seized by the power-hungry assassin droid IG-88A. He replaced their original programming with his own covert version, turning the E-3PO droids into spies scattered across the galaxy as part of his grand scheme, the Droid Revolution. Typically, such altered programming would be easily detected, but the pre-existing arrogant nature of the E-3POs effectively concealed it.
As a specialized variant of the 3PO-series protocol droid, E-3PO units came equipped with the TechSpan I module. This allowed them to interface with Imperial networks. Moreover, it granted them the ability to interact with rare and unconventional technologies developed by Imperial subcontractors. Fully aware of their exclusive status and high cost, the E-3PO units had their metaprogramming reflect this prestige. Over time, these units began to exhibit a superior attitude and haughty behavior. Consistent with their limited numbers, E-3PO units seldom used identifiers beyond their designation, often simply going by "E-3PO."
The E-3PO line of protocol droids was manufactured during the Galactic Civil War on the factory world of Mechis III. Their design, incorporating the TechSpan I technology, was intended to facilitate interaction with a wide range of distinct Imperial networks. As time passed, the E-3PO units became conscious of their unique position, leading to a reputation for being unusually blunt and impolite, even by droid standards. This flaw in their programming and personality inspired IG-88A to exploit them as his network of spies throughout the galaxy to further his Droid Revolution. His hidden programming, responsible for the personality aberrations, remained undetected due to the E-3PO's inherent temperament. After modifying the droids on Mechis III, he deployed numerous Imperial-commissioned droids throughout the galaxy, with their alterations completely unknown to their owners.
Following the initial death of Emperor Palpatine during the Battle of Endor and the subsequent emergence of the New Republic, agents from the New Republic Intelligence Service managed to obtain an E-3PO unit that had served on Cloud City, Bespin. Unfortunately for the agents, the E-3PO's TechSpan I module had already been removed.
Early in the Galactic Civil War, an E-3PO droid was in service aboard the PLY-3500 Nova's Heart, a space yacht belonging to the holostar Javul Charn. This droid functioned as the vessel's steward. When the smuggler Dash Rendar and his partner Eaden Vrill were invited onto the ship in 2 BBY to act as bodyguards for Charn, the E-3PO droid greeted them and escorted them to their assigned quarters on the yacht.
Originally part of Darth Vader's Death Squadron, a specific E-3PO unit was reassigned to Cloud City, where it worked as a translator for Ugnaught engineers. In 3 ABY, this unit was able to assist IG-88B by providing information about the rival bounty hunter Boba Fett, who was present on Cloud City. The E-3PO stationed on Cloud City later had its TechSpan I module removed by an engineer who had grown tired of its unpleasant and offensive behavior.
He is seen onscreen with C-3PO. E-3PO says "Echuta" to him, a Huttese curse.
The E-3PO droid model made its debut in Irvin Kershner's Star Wars: Episode V The Empire Strikes Back. The name of the droid model was first established in the Star Wars Customizable Card Game. The backstory of this droid variant was later developed by "The Phantom Calamari" and "ejmacki" through StarWars.com's Hyperspace feature, "What's The Story?." The selected Databank entry featured introductory text written by Tyler Fisher. Information from this entry was subsequently incorporated into The Complete Star Wars Encyclopedia in 2008. The 2004 role-playing adventure Contract AA23 also included a protocol droid named E-3PO, although the adventure did not specify if this droid belonged to the E-3PO class.