How can you give guys butterflies?

I wonder if this "butterflies" phenomenon is unique to females. I know many times I've had a pleasant but nervous feeling when I first met a girl that I liked, and knew that she liked me back. Mutuality is a beautiful thing. But I've never understood why girls call it the butterflies. So if the question is, "how do I make a guy like me?" then I would say just flirt with him a little and see what happens. If he breaks out in a rendition of "Singing in the Rain" then you know you've had that effect on him.