Plumbob

A PlumbBob is used in most titles of the Sims series to identify the character selected. It is also used to show the mood of your Sim. In The Sims 2, the plumbbob is white if the Sim has a very high mood, bright green if the Sim's mood is high, bright red if it is low, or if mood is somewhere in between then it will be a shade of green-yellow reflecting the approximate level.The PlumBob is featured through all Sims games and in The Sims it barely ever changes.

Perma-platinum can be achieved through completing the Sim's Lifetime Want if the player has Nightlife through Bon Voyage, however if the player has FreeTime perma-platinum can be reached through completing the life achievement bar.

Also in The Sims 2, Sims who belong to the same active group as the selected Sim will have a smaller plumbbob over their head. This plumbbob is blue, irrespective of mood.

Plumbob to a Sim
According to the "Atlas's Burden" statue in The Sims 3, the PlumBob is a tangible representation of the "celestial weight" (the player) controlling the Sim's world.