She was voiced by Nora Dunn.
Precious was a simple house cat who belonged to Dr. Mordough, a scientist who built the gene splicing machine that turned Snowball, Pinky and The Brain into lab animals that can talk and are intelligent. She gained brainpower from being accidentally sent into the gene splicer just like Pinky, Brain and Snowball. She swore vengeance on humanity due to losing her feline beauty.
Unlike Brain or Snowball, Precious did not have a plan of ruling anything, she just wanted to destroy the whole humanity and bring everything to ruin out of revenge and anger.
After her plan was foiled, she was taken in by Bobby Bob Boffo, who called her "the purtiest kitty he's ever seen". She later redeems herself by sending Pinky and The Brain an apology letter and thanked them for helping her find a happy and loving home.
The Brain noted Precious would consort with a less dangerous bunch of clowns after Bobby Bob got promoted to Chief of Staff.