Sims

Sims are the simulated people that form the base of nearly every Sim game, however you can only interact with them greatly in The Sims and its sequels. Sims were first mentioned in the first edition of SimCity but never could be seen. Their first known appearance was in SimAnt (1991), where they were the owners of the yard the ant colony lived upon. Apparently the first "seen" Sims were a Black man, his dog, and a boy which is assumed to be the man's son. You can also see a stray or wandering cat outside the yard that the dog frequently scares away.

Further interaction was given to the Sims in SimTown (1994), and was the base of many concepts that later went into The Sims. Among these, a very basic mood meter was introduced (it just contained "sad" and "happy" and had relatively few factors go into it), you could choose certain Sims' favorite things (somewhat like Aspiration in The Sims 2), and you could actually pry into all houses (only one floor could be revealed, however).

After that, no game quite got as close to The Sims as the game itself. However, Streets of SimCity (1997) introduced Simlish for the first time in the radio music. The first game with spoken Simlish was SimCopter (1998).