Long-a-go and far-a-way?

In a similar vein to the mistake that people make with "sing-along" I have also noticed "look-a-like". There is even a TV show called this, mistaken hyphen and all. What is so hard to understand? One person looks like another. They look alike. You can even call them "lookalikes". Look-alike or lookalike. NOT look-a-like!