As a Brit, I’m not sure what a ‘Karen’ is, but it sounds like a younger, female version of what we would call a ‘Victor Meldrew’ -an arrogant, curmudgeonly, elderly man who is always ready to complain about poor service and browbeat those he holds responsible.
I never thought about this until my wife informed me some years ago that I have an alter-ego she calls ‘the Major’. It seems that when faced with inattentive or incompetent staff, high-pressure sales- talk or cold calls, I change. My Yorkshire accent vanishes, and I acquire a tone of command that makes people jump to it. Apparently any number of difficult situations have been resolved by the arrival of ‘the Major’, but he used to scare the kids. “Dad’s being polite again!” They’d whisper to each other, before abandoning mischief, squabbling and asking too many question for at least an hour! I never realised.