The sneaky sperm cells all come like a thief; packed with all the tools of its trade carefully well hidden. Once inside the house or egg, it brings out all the tools (unzips if you will) and starts work.
Above is exactly what was going through my mind as I read this post. Now I know it is not only .rar and .zip files that are compressed :)
zip, unzip, sperm, egg......... everything is already adding up :)