
Leonard, in the world
of THEORETICAL physics, you never finish.
The Big Bang Theory Season 10, Episode 15

as a THEORETICAL
physicist,
The Big Bang Theory Season 7, Episode 20

...THEORETICAL physics is... What's the word
I'm looking for? Hmm, cute.
The Big Bang Theory Season 4, Episode 3

She's a neurobiologist, and
I'm a THEORETICAL physicist.
The Big Bang Theory Season 7, Episode 21

Now to tell you about
the Theoretical Physics Department...
The Big Bang Theory Season 2, Episode 6