In 2268, the USS Enterprise arrived at Platonius. Enterprise chief medical officer Leonard McCoy determined that the others got their power from the food native to Platonius which contains Kironide, a substance that after being assimilated by the pituitary gland promotes psychokinesis. Something in Alexander's metabolism had kept him from acquiring the powers.
When the Platonians refused to let the crew leave so that they could be used as slaves, and for amusement, Alexander helped the Enterprise crew escape. McCoy synthesized the kironide and injected himself, Kirk and Spock. Alexander refused to get a dose, because he did not want to become like the other Platonians. Parmen, the leader of the Platoians, tried to use Alexander to kill Kirk. He forced him to try and stab Kirk, but Kirk whose powers were now stronger, turn Alexander around and he approached Parmen with the knife. Alexander wanted to kill Parmen, Kirk refused to allow him to do so. Afterwards, he would depart Platonius aboard the Enterprise. (TOS: "Plato's Stepchildren")
- Alexander was played by actor Michael Dunn.