Hydrogen.
The Big Bang Theory Season 12, Episode 23
A HYDROGEN atom, H,
plus pigs minus P, "higs."
The Big Bang Theory Season 3, Episode 13
Didn't you say you're making
HYDROGEN sulfide gas?
The Big Bang Theory Season 4, Episode 4
they theoretically can separate
the HYDROGEN from the oxygen,
Breaking Bad Season 2, Episode 12
HYDROGEN was a little more
common or a little less common.
The Big Bang Theory Season 7, Episode 5