SHELDON: All I did was answer
a few questions about the THEORY.
The Big Bang Theory Season 8, Episode 18
in a world still governed
by string THEORY.
The Big Bang Theory Season 12, Episode 5
I guess we wait until they're old enough
and let them choose their own THEORY.
The Big Bang Theory Season 2, Episode 2
AMY: Previously on
The Big Bang Theory...
The Big Bang Theory Season 10, Episode 5
They're forcing me
to continue with string THEORY.
The Big Bang Theory Season 7, Episode 24