What some people might forget is that there is a difference between being illegal and being sued. Making a fangame is by definition always illegal. But as long as you're unknown and not public (especially as the original licence holder doesn't know about you), then you can continue your work at your own risk. That risk comes into being when the original licence holder detects your work. And then he can choose what to do about it. SOME companies might like your work and give you the licence to use their property (with or without written contract, with or without payment or other agreements). And as soon as you get that licence, you're no longer a fangame but a licenced game and legal. SOME companies will prefer to ignore your work, still pretending it doesn't exist to avoid the hassle of legal contracts (usually only in countries where copyright is not voided by allowing illegal use). SOME companies will inform their lawyers and force you to remove and delete your fangame - sometimes even suing you with damages for illegal use of their trademark. And now think about this: A lot of people do fangames because they want to boast about them ("look what I have done"). But the more publically known you are, the higher the chances of your work being detected by the licence holder, resulting in higher chance of being sued for your work. So if you hope not to get caught, then this means you have to hope not to get known for your work through the internet. Which means you can't boast about your game anywhere.... It's easier in the long run to come up with your own ideas if you want fame.