I've searched and was surprised there wasn't a thread dedicated to MUGEN.
For those who don't know, MUGEN is a highly customizable Internet Fighting game where you make it any way you want. As long as the character and stages exist.
Say you want Mario to fight Ryu from Street Fighter, you can make it happen. If you want to put Homer Simpson in a fighting game, then you can make it happen. As long as you can find it and download it and put it in your MUGEN game.
Now, I'll provide some basic links for those who want to get started.
Here you download WinRAR, you need this not only to download MUGEN itself, but everything involving characters, stages, screenpacks, ETC.
Here's where you download MUGEN. That's pretty much it.
Best MUGEN site ever. Click Database for links to many MANY characters and stages.
For tutorials on how to know how to work it. Go to YouTube, there's tons of Tutorials there. I'm not going to say which is the best, but you'll figure it out.
So now, let the battle of history unfold.