Who Mourns for Adonais? - S2-E2
Revealing mistake: When Apollo first grows large, the shimmering edge of the special effects matte is visible in the sky just above his right shoulder. (00:13:35)
Who Mourns for Adonais? - S2-E2
Revealing mistake: As Apollo's head and neck appear on the screen, the neck of the black T-shirt used to mask his body is easily seen, and his shoulders are faintly visible.
Answer: Kirk was getting his physical and Dr. McCoy probably turned off communications, because if he hadn't, Kirk would have left and headed straight for the bridge, leaving McCoy irritated.