Zodiac sign

When creating a new Sim in The Sims and The Sims 2, the Sim will be given the Zodiac sign that's closest to the personality that was chosen. As the player assigns and reassigns personality points, the display will change to show which sign the Sim will have with that mix of points.

In The Sims 2, players also have the opportunity to select a sign from the Zodiac, and use the preset traits for that sign as a starting point. Personality traits affect not only the things Sims prefer to do, but also their relationships. In The Sims 3 this was replaced by a Traits system.

Sims will generally get on well with other Sims who have the same sign. "Attracted to" and "disgusted by" are not absolutes, but modifiers that help or hinder the growth of a relationship. Sims with incompatible signs can become good friends, and even lovers, if they have enough else in common. However, it'll take longer, and they'll have to work at it harder. Likewise, Sims with compatible signs but little else in common will have trouble building a relationship, and may even end up becoming enemies.

Late Night
According to a preview from "Sim Cookie", zodiac signs will return in The Sims 3: Late Night, though it is unknown it will affect attration between Sims or other mechanics