- See Brennan for other articles with titles that contain, either by relationship or by coincidence, this character's surname.
In 2268, Brennan replaced Leonard McCoy as a member of survey team that traveled to the tropical planet Tau Omega III aboard the Copernicus, which crashed after being disabled by the electromagnetic pulse of a solar flare. Lieutenant Commander Francis Greelee asked Brennan and pilot Lewis Baker to remain by the spacecraft while the rest of the crew scouted the jungle. Brennan asked if Baker would be able to repair life support in the wreckage to give them a break from the sweltering heat, but all systems had been burned out.
Later, while Brennan was inside, a large omegasaurus overturned and crumpled the shuttle, killing him. The landing party was able to extricate him from the wreckage and make him a temporary gravesite. (TOS - FASA RPG short story: "Planetfall")