I imagine you understand 'we all know how the movie ends and 'Ted falls in love' so let's look at the other two parts: to kick someone in the sprouts - probably a reference to a man's testicles so Ted was kicked in the balls by love meaning that, Ted in a vunerable position by being in love, was caught by surprise and/or hurt. The credits roll - the list of the people as the end of the film (actors/producers etc) - meaning the film ends.