Japanese kids in candy or toy shops scream " onegai, onegai, onegai" when they want mom or dad to buy something. So I guess it can be translated as "do it for me or you'll never hear the end of it."
My wife says it about the third time she repeats a request. Would you do that?
Would you do that thing I asked?
Then, yes, it's do it or you'll never hear the end of it!