7 Times Someone Caught The Idiot Ball In Star Trek II: The Wrath Of Khan
3. No One Listens When Chekov Says He's Been Compromised
Early in the film, in a scene that’s pure, delicious horror, Khan puts a couple of creepy crawlies in Terrell and Chekov’s ears to make them malleable and compliant to his demands. This turns the young Russian into a willing, if not mildly zombie-like, pawn in Khan’s revenge scheme.
Part of that scheme includes leaving Chekov and his captain in a space-locker for Kirk to find so the two can double-cross him. And it would have worked, too, if Chekov hadn’t opened his big mouth and told the whole rescue party that he and Terrell had "creatures in [their] bodies" to make them "do tings!"
Oh wait, the plan did work because no one bothered to listen. Kirk doesn’t pay attention. McCoy doesn’t give them a medical scan to see if the creatures are indeed there and what influence they could still be having. Even constant rule-quoter Saavik doesn’t bite. They just let the two zombies join the team like it’s no big deal.
Because of this lapse Terrell and a scientist die, Kirk is almost zapped himself, and Khan makes off with the Genesis device.