Life state

Each expansion pack for "The Sims 2" released to date has added an alternate state in which Sims can exist. These states have unique triggering techniques, advantages and disadvantages. These states are:

Aliens
Zombies
Vampires
Servos
Werewolves
PlantSims

Each life state offers up a new oppertunity for the sim and the player, making certain aspect of play easier to handle and others harder, for example a vampire with a night job.

There are also many story oppertunities with these states.