Available now for free, this update brings the spooky addition of Ghosts to The Sims 4. Your dead Sims can now rejoin the world of the living, where they maintain all the attributes they had a as a Sim, but with special new behaviors based on how they died. If you invite them to join your Sims' household they can be playable characters; if you dare, you might even find a way to bring your ghosts back to life.
For example, ghosts that die from laughter stay positive, with a moodlet causing nearby Sims to become playful. Sims that have been electrocuted to death will become ghosts capable of breaking objects by possessing them. Victims of the Cow Plant spend the afterlife interested in gardening; if you are lucky, a ghost will lovingly tend to your Sim's garden, but a bad mood will lead to a yard full of dead plants.
A video and three presenting this new content are available for your viewing pleasure.