
I believe the appropriate METAPHOR here
involves a river of excrement...
The Big Bang Theory Season 2, Episode 8

Yeah, me, too. I was stuck for a METAPHOR.
The Big Bang Theory Season 9, Episode 12

It's a sports METAPHOR.
The Big Bang Theory Season 2, Episode 7

Wow, was that your first ever
sports METAPHOR?
The Big Bang Theory Season 12, Episode 10

I believe the back-scratching METAPHOR
describes a quid pro quo situation...
The Big Bang Theory Season 2, Episode 16