my favorite is "not a Scooby" in place of "haven't got a clue"
I use it often stateside and get weird looks
It's a common mockney rhyming slang, it follows some principles of cockney and is now used by most people, BUT it's not 1840s - 1920s and it gives a clue to what's being said, that scooby looks for clues and scooby is not a common word.
Apples and pears have nothing to do with stairs.
Butchers hook has nothing to do with a look.
Going up the apples to have a butchers.
One for anyone to try out guessing:
My Trouble don't like me Raspberries
(I use berk all the time not realising it's cockney for Berkshire Hunt)