ES-PSA, also known by the moniker Espasa, was a RIC-920 rickshaw droid that came from the production lines of Serv-O-Droid, Inc.. He functioned as a rickshaw operator in the spaceport located in Mos Espa on the planet Tatooine, specifically during the period encompassing both the Separatist Crisis and the subsequent Clone Wars.
The ES-PSA unit was constructed to be a multi-purpose labor droid, equipped with very basic programming that allowed it to perform simple duties. Ultimately, it became one of the many RIC-series droids working as rickshaw drivers within Mos Espa. ES-PSA, powered by a set of disc-shaped treads, pulled an unpermitted rickshaw through the crowded streets of the spaceport.
Before the Clone Wars began, ES-PSA provided transportation for Anakin Skywalker and Padmé Amidala, taking them from a docking bay within Mos Espa to Watto's shop for junk, during Skywalker's quest to find his mother.
When the script for Attack of the Clones was being written, George Lucas realized that Anakin and Padmé needed a means of transport to get around Mos Espa. Initially, Jay Shuster had imagined an Otoga-222 maintenance droid performing the rickshaw-pulling task.
Marc Gabbana finalized the design of the RIC-920. While it was intended to pull the repulsorlift rickshaw, Gabbana thought of the droid and the vehicle as separate things that were only joined together out of necessity, not by initial design. In the final version of the film, RIC-920 was created entirely using computer-generated imagery.