An outmoded THEORY, of course.
The Big Bang Theory Season 2, Episode 15
Previously on
The Big Bang Theory...
The Big Bang Theory Season 11, Episode 15
Just explaining the THEORY of relativity.
The Big Bang Theory Season 6, Episode 5
our THEORY still stands.
The Big Bang Theory Season 12, Episode 10
Or in layman's terms, string THEORY.
The Big Bang Theory Season 3, Episode 14