Robert Johnson is a scientist of the Gamma Hydra IV expedition found in The Deadly Years as a frail old man although he is only twenty-nine, a victim of the accelerated ageing disease.
Robert Johnson is a member of the scientific party on Gamma Hydra IV visited by the Enterprise in the Original Series episode The Deadly Years. When the landing party arrives for a routine resupply, he greets them as a deaf, shrunken old man.
Johnson tells an astonished Kirk that he is twenty-nine years old and that his wife Elaine is twenty-seven. The other members of the expedition have already died of what looks like extreme old age.
The Johnsons are taken aboard the Enterprise, where both soon die. Their case gives McCoy his first look at the radiation sickness, carried by a passing comet, that then begins to age Kirk, Spock, McCoy, Scott and Lieutenant Galway.