What's Nick Cannon's safe word? Kevin Hart pushes all of his buttons til we find out. -- Celebrity Prank Wars: When Nick Cannon sent Kevin Hart an actual, real live llama to his house as a birthday present… it could have been “one and done” and well played by Nick. But it wasn’t. Kevin Hart retaliated by paying for several very expensive billboards in several major cities displaying Nick Cannon’s private cell phone number. This story made headlines across the country. It was so funny and unexpec