
Previously on
The Big Bang Theory...
The Big Bang Theory Season 11, Episode 11

You want me
to give up string THEORY
The Big Bang Theory Season 7, Episode 20

Gentlemen, is anybody interested
in my old string THEORY books?
The Big Bang Theory Season 7, Episode 20

that proves their THEORY wrong.
The Big Bang Theory Season 12, Episode 9

you used to disprove his THEORY?
The Big Bang Theory Season 7, Episode 10