Kaplan

We don't know technically why, but the title does seem to be Mr. Kaplan's preference.

Season 2, episode 2 "Monarch Douglas Bank", Red gets frustrated with Mr. Kaplan and sharply calls her "Kate" -- this rattles her, and Red later apologizes.

Then there was this comment from season 2, episode 3, "Dr James Covington":

Red: Remember the time we made barley stew with that coroner from Des Moines?
Mr. Kaplan: It was Reuben soup. How can I forget? I was sleeping with his sister.


Just from past friendships, I know there are degrees of transgender identity-- For example, there are physical females who prefer to be referred to as 'he' not 'she'. And yet, they have no intention of actually getting gender reassignment surgery, they just prefer the dialogue, etc, to refer to them as men. I think it's implied that Kaplan is a lesbian, and falls into the category where she prefers to identify as a man.


Sometimes fires don't go out when you're done playin' with them.

I've never heard anyone that had a provable answer but the best reason I've heard and the one that I believe is that in "North By Northwest" the man who didn't exist, that Cary Grant's character was mistaken for was called Mr. Kaplan. That's the reason that I'm convinced is true.

I believe they call Kate ,Mr Kaplan because. her husband was the original Mr Kaplan and when he died or was killed she became the new cleaner . Taking the place of her husband as proof to Red that she was just as capable of doing the job as her husband . instead of changing all the info on his "cleaner" button on his phone . Red just left it to what it was , the number he called and what he said to activate the cleaner . as a joke he just kept saying " Mr Kaplan " and Kate just played along .