You can't change the PIN?
KEF is good stuff, I normally would have said that if you are in the market for such a product, buy it.
I'd probably prank entirely differently, if one of my neighbors had a KEF Egg. I'd probably transmit Testtone, then occasionally overdub subliminal messages, like "Don't vote for Trump, ever again" and "quit breeding" and "get a vasectomy" and "quit beating your wife" and "quit cheating on your husband" and "don't knock gay sex until you've tried it"...