In 2332, as a Starfleet Academy cadet, he was assigned to the USS Enterprise-C. After the death of helmsman Aine McAvennie during an attack by unknown aliens, Castillo took the helm position. (ST short story: "Hour of Fire")
Castillo remained on the Enterprise for twelve years, eventually reaching the rank of lieutenant. In 2344, the Enterprise was caught in a battle with the Romulans, and was sucked into a temporal vortex and deposited 22 years in the future. Intercepted by the USS Enterprise-D, he met Lieutenant Natasha Yar, and began a relationship with her. Following the death of Captain Rachel Garrett, Castillo was the last surviving senior officer. He and Yar took the Enterprise-C back into the past to defend the Klingon world of Narendra III, where the ship was destroyed (TNG episode: "Yesterday's Enterprise")
- The novel Vulcan's Heart has Castillo taken captive by Romulans, and killed shortly thereafter by a Romulan commander for insolence. The short story "The Fourth Toast", however, has Castillo still alive into the 2360s.
|USS Enterprise-C personnel|
|Alfonzo • Aria • Aristide • Bat-Levi • A. Batra • Bulast • Carmona • Castillo • Chu-Fong • Cohen • Coron • Donald • Fredericks • Garrett • Thule G'Dok Glemoor • al-Halak • Hemachandra • Holmes • Junior • Katie • Kepler • Kodell • LoPresti • Luttrull • McAvennie • Norrie • Parker • Singh • Singh • Stern • Stewart • Tholav • Tyvan • Varani • Vinson|