I believe the back-scratching METAPHOR
describes a quid pro quo situation...
The Big Bang Theory Season 2, Episode 16
Yeah, me, too. I was stuck for a METAPHOR.
The Big Bang Theory Season 9, Episode 12
I believe this is an extension
of the death METAPHOR.
The Big Bang Theory Season 2, Episode 8
...the terms of your METAPHOR
by acknowledging her existence. I'm out.
The Big Bang Theory Season 2, Episode 8
Wow, was that your first ever
sports METAPHOR?
The Big Bang Theory Season 12, Episode 10