Zombie

Congratulations! By some fortune, you are now the walking dead! You can tell you are by looking at your green and rotten skin, and checking whether you feel a craving for brains. Zombies like you don't usually appear unless the gods will it, so go hog wild on the crew (who are probably armed with shotguns and flareguns and other devices of inflicting pain upon your undead flesh). Player-controlled zombies can't multiply their numbers by eating brains anymore, however. You look scary, can reanimate indefinitely unless gibbed, walk much slower than a normal human, can't speak without anything you say coming out as "Braiinnnnnssss", and (unlike NPCs) cannot survive in the cold void of space without protective clothing and oxygen supply. That's about it.

There are also non-player zombies to be found in the darkest corners of space. They are pretty dangerous unless you have a heavy blunt object or a phaser, in which case they explode spectacularly into a rain of gibs. NPC zombies can spread, by (under normal circumstances) first knocking down a crew member, and eating their brains. About three seconds later, the player of the unfortunate crew member will be kicked out of their old body, as it is now another NPC zombie, just taking the name of the owner of the corpse it now controls.