This phrase is best effected when accompanied by knocking on the forehead of the doofus you're making fun of, proceeded by multiple hellos, and followed up by asking if anybody is home.
Hello... Hello... Hello McFly! Anybody Home?
Actually, I hear people say this all the time. I've heard it at least once a week ever since about 1985 or so, when Biff Tannon first rapped on the forehead of George McFly because McFly didn't give Biff enough time to copy his extorted homework. The origin of the phrase was a movie called Back to the Future (sort of - I'll explain shortly). People say this to sarcastically point out that someone has not thought something all the way through, and are fixin' to step on their crank.
A quick websearch on Google shows that even 15 years later this phrase is still popular and in common use. Of course the abbreviated form ("Hello?" sans McFly) is a common vector.
Not too long ago, I was sitting around, thinking about this phrase, because that's the sort of thing people like me sit around and think about. And it occurred to me that I don't actually remember hearing Biff say those exact words. So I watched all three movies in the trilogy, and I discovered that Biff, never actually said, "Hello McFly."
One of the most popular phrases of a generation is based on a misquote.
I was crushed.