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

Not a METAPHOR,
not an analogy,
it's a...
Breaking Bad Season 2, Episode 10

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

I believe this is an extension
of the death METAPHOR.
The Big Bang Theory Season 2, Episode 8

Luckily for you,
that's where the METAPHOR ended.
The Big Bang Theory Season 1, Episode 15