Why can't the british say "plop"?
"Plop, plop, fizz, fizz, oh what a relief it is." became "Plink, plink, fizz, fizz..." in the UK!
Methinks the British have way too many slang words for "number two". Plop shouldn't be one of them. If that is what plop means, I'm just guessing here. But that's probably it.
Speaking of, have some chocolate.