
But I find that TOPIC irresistible so,
The Big Bang Theory Season 10, Episode 7

Okay, the first question
is on the TOPIC of optics.
The Big Bang Theory Season 1, Episode 13

So, Alex,
what's the TOPIC of your dissertation?
The Big Bang Theory Season 6, Episode 3

This is an interesting TOPIC.
The Big Bang Theory Season 4, Episode 1

Okay, literally any other TOPIC.
The Big Bang Theory Season 10, Episode 16