S-4 functioned as a quarantine inspector droid for the Star Tours travel company. Alongside his partner, P-6, he maintained the cleanliness of the baggage claim zone. His equipment consisted of radar, a magnifying glass, and a flyswatter. Their supervisor was a blue R2 unit. For movement, he needed locomotive pads.
Information regarding this particular droid is sourced from a "Spot the Droid" poster that was on display at the Star Tours attraction in Tokyo Disneyland. This information was translated by the fan website EndorExpress.net. The Complete Guide to Star Tours booklet also provides information. This droid was there on the first day the ride opened, but later he and his partner, P-6, were taken away. The "droids" were actually industrial robots that had been modified.