Making jokes is always fun but it is imperative that the victim has a sense of humour to avoid all kinds of problems. As the world has evolved with the advent of computers and advanced technology, jokes have also taken other forms. Fly On Desktop is a program that allows you to a colony of a dozen flies that looks like real flies on a computer screen. It can be installed without the knowledge of the user. It starts at the same time as the operating system. You can configure it for more realism or even to upset more the victim. It is important to note that it is completely harmless except for the nerves.