Lithium

Lithium is one of five robots mistakenly created by Bartman at Professor Frink's laboratory. She resembles Lisa Simpson, and is made of the metallic element.

History
Professor Frink had a vat ready to create metal robots based on a single element, and he was waiting for the perfect DNA to encode their personalties from. Bartman, standing near the VAT with a bag of laundry in his hand, accidentally set of his new sneezing powder Batarang, causing him to drop the bag into the vat. Suddenly a large explosion occurred and five robots appeared, based on the Simpson family.

Professor Frink called them corrupted, which, according to Holmium, "are fighting words", leading the robots to go off on a rampage. The robots visited the Kwik-E-Mart, Bartman tried to take them back to Frink's laboratory, but the robot's used their elemental features to counteract his moves. Lithium used her weightless to trick Bartman to jump into the poolmobile.

Due to the similarity to his family, Bartman decided he couldn't hurt them, and they felt the same way. At that time, Gastro, a mutant created by Homer dropping his lunch bag into a radioactive vat, arrived causing chaos, which Bartman and the robots teamed up to defeat. Lithium, with the rest of the robots, tried to defeat it, but due to the large amount of chemical preservatives, they were insufficient. Bartman got Apu's expiry date changing sticker gun, and used it on Gastro, marking it to expire May 1995, causing him to blow up.

Later, back at the lab, the robots were in a glass box set-up, with a metallic version of the Simpsons' living room.