It's string THEORY.
The Big Bang Theory Season 11, Episode 14
Excuse me, but a grand unified THEORY,
insofar as it explains everything...
The Big Bang Theory Season 4, Episode 3
some big string THEORY news
today
The Big Bang Theory Season 7, Episode 20
I guess we wait until they're old enough
and let them choose their own THEORY.
The Big Bang Theory Season 2, Episode 2