I believe the back-scratching metaphor
describes a quid PRO quo situation...
The Big Bang Theory Season 2, Episode 16
Dr. Sheldon Cooper appearing in PRO se.
That is to say, representing himself.
The Big Bang Theory Season 3, Episode 16
FYI, part of your responsibilities
as roommate PRO tem...
The Big Bang Theory Season 4, Episode 24
- Where do you stand on it?
- Strongly PRO.
The Big Bang Theory Season 6, Episode 1
lt behooves you to be a PRO,
that's all. That's the fiction.
So chop-chop.
Breaking Bad Season 4, Episode 4