Clem is a harmless anaphasic lifeform whose attempts to communicate make the Cerritos crew behave like zombies aboard Starbase 80.
Clem is an anaphasic lifeform that the Cerritos unknowingly picked up on a previous mission. In Starbase 80?!, the ship docks at the notorious starbase and members of the crew begin acting like zombies, convincing Mariner that the station is cursed.
The phenomenon turns out to be Clem, who has been possessing crew members in failed attempts to communicate. Once it is clear that Clem means no harm, the lifeform is invited to remain at Starbase 80.