You know what? I'm thinking Howard
wasn't making a back-scratching METAPHOR.
The Big Bang Theory Season 2, Episode 16
Luckily for you,
that's where the METAPHOR ended.
The Big Bang Theory Season 1, Episode 15
Wow, was that your first ever
sports METAPHOR?
The Big Bang Theory Season 12, Episode 10
That was a beautifully written
penis METAPHOR.
The Big Bang Theory Season 5, Episode 1
I believe the back-scratching METAPHOR
describes a quid pro quo situation...
The Big Bang Theory Season 2, Episode 16