Plastic
From Tardis Wiki, the free Doctor Who reference
Plastic is an artificial substance created on Earth by Humans to make such items like maniquinns, phones, cables, and breast implants. Plastic has no real value to beings unlike gold or silver.
The Nestenes are able to inhabit and animate plastic, giving them the identification of living plastic creatures. (DW: Spearhead from Space, Terror of the Autons, etc)
