The shaving cream atom, supplies of which become dangerously low on Earth in the 24th & 1/2 century, necessitating a mission by Duck Dodgers to claim Illudium Phosdex-rich Planet X in the name of Earth.

Not to be confused with its unstable isotope Illudium Pew-36

Adj. Something that is expected to have a long lifespan by virtue of having existed for a long time, based on the lindy effect, named for the New York restaurant Lindy's, coined by Albert Goldman and popularized by Nassim Taleb.