Cut the watermelon slices into stars using cookie cutters. I like to use a few different sizes so they look better on the platter. Set aside.
Beat together the cream cheese, marshmallow fluff, and vanilla in a medium mixing bowl. Transfer to a dip bowl for serving.
Place the fruit dip onto the platter and arrange the watermelon stars and blueberries around the bowl. You can also skewer the watermelon and blueberries onto wooden skewers to make fruit kabobs if you prefer. Chill until ready to serve