Our three and a half year old girl learnt the choice phrase "Fark Sake". She would say it over and over and over again. My wife couldn't help her self and would crack up every time she said it.
I had to sit the little one down and teach her that we don't say those word and instead we should say "oh my goodness!'
A week later she is sitting at the kitchen bench having breakfast. My wife comes in from walking the dogs and my daughter suddenly pipes up and says, "I don't say Fark sake, I say Oh my goodness", she repeated this four or five times and I had to go and pick my wife up off the floor because she could stop laughing.