- See Rizzo for other articles with titles that contain, either by relationship or by coincidence, this character's surname.
- For the mirror universe counterpart, see Rizzo (Ensign) (mirror).
In 2268, Rizzo led a security team on the planet Argus X. When Kirk smelled a familiar scent, he asked Rizzo to search the perimeter for dikironium with two men, and shoot immediately into any gaseous clouds. Rizzo was puzzled by strange readings on his tricorder. He hesitated when a white gas started choking his men, unsure of where to fire his phaser, before the dikironium cloud creature enveloped him as well. Rizzo was left barely alive; his men had been murdered.
Blood transfusions failed to help the dying officer, who had been drained of corpuscles. Kirk asked Leonard McCoy to revive Rizzo for a moment to confirm suspicions about the cloud, and 1 cc of cordrazine was injected into him. Later, he died from his injuries. (TOS episode & Star Trek 9 novelization: Obsession)
- Rizzo was identified as a lieutenant in the novelization, but wore an ensign's uniform in the episode. One of his men was Ryan Leslie, who was depicted as having perished in the episode despite having several subsequent appearances.
Later that year, while feeling as if he might be mortally wounded, McCoy recalled Rizzo, his father David Andrew McCoy, and others he'd been unable to keep from dying. (TOS novel: A Choice of Catastrophes)
In 2267 of an alternate timeline where Human women held slaves, Rizzo served aboard the HMS Enterprise. He and Beggs Hansen witnessed the death of James T. Kirk. (ST - New Visions comic: "The Mirror, Cracked")