Kirk, Spock, McCoy and Yeoman Rand arrive on a planet resembling Earth in the 1960s and discover it has been ravaged by a genetically engineered virus that kills adults and extends childhood. Many of the children who appear in this episode are William Shatner’s, Gene Roddenberry’s and director Vincent McEveety’s actual children. Miri: Kim Darby. Jahn: Michael J. Pollard. Fat Boy: John Megna. Kirk: William Shatner.