
One time my brothers
made me breathe HELIUM.
The Big Bang Theory Season 12, Episode 6

Not quite accurate.
The Macy's balloons are filled with HELIUM...
The Big Bang Theory Season 4, Episode 24

the abbreviation for HELIUM.
The Big Bang Theory Season 7, Episode 3

You see, instead of
using liquid HELIUM...
The Big Bang Theory Season 11, Episode 8

"Helium."
The Big Bang Theory Season 2, Episode 5