OR: The one project that will probably (read: hopefully) Never be completed.
A somewhat simplified version of the other one, hopefully easier to read.
When a line passes through other lines, but doesn't touch them, it's not meant to have anything to do with them. When a line splits, all things it points to are linked. When you see those coloured lines, don't freak out or anything, especially about how they've been cut or something, it's just that I couldn't find a way to wrap them around the huge great big middle part of the image.
Mario is six steps removed from dragonball.
EDIT: Okay, so some people have asked me exactly what this means in terms of what's in what world.
I'll try to explain.
There are two kinds of links here.
First, a link from one series to the other. IE; Mario to Zelda. However, both Mario and Zelda link to other series, too. I find that it is least mind-bending to, when writing a crossover, specify how many steps apart you want to take it. As in, saying: "I want to make a Mario and Zelda crossover, and everything that they directly link to will be in it too." Or, "I want to make a Mario and Zelda crossover, and everything up to one step further will be in too." Doing so takes the pressure off a writer far better than would be otherwise able, as you might feel that you absolutely MUST put in a reference to all of those things, or worse, absolutely MUST make a character of all those things and MUST give them equal screen-time. Which, unless you're doing a Baton-Passing sort of story, will very rarely end well.
Lastly, a link that links to a specific crossover, like Acadamy Of Champions, or Battle Stadium D.O.N. Seeing as how these characters have canonically appeared as themselves together, one may take this to mean that those characters co-exist in their universe. IE; if you link to Assassin's creed, you basically link to Rayman, Splinter Cell, Prince of Persia and Beyond Good And Evil as well. The other examples of this are The Infestation, Cartoon All-Stars To The Rescue, Sega Crossovers, Mario&Sonic, Mario Kart/DK Racing Games, Freddy Vs. Jason Vs. Ash, Marvel Vs. Capcom, Street Fighter X Tekken, DC Vs. Mortal Kombat, and Avengers Vs. JLA. (Note: The League Of Extraordinary Gentlemen MIGHT count as this, depending on how lenient you are with the source material. Either it Retcons all the different universes together, or it is essentially fanfiction itself).
Special Note: Super Smash Bros. is not on this list, because all the characters represented in it are essentially only toys of the characters they represent, and therefore you are not literally playing as Link, or Pikachu, or Mario. It was always like that. It's essentially the same reason as Metal Gear not linking to Mario, despite having references to it: It is not an In-Universe crossover. Luckily, the majority, if not all, of Smash Bros. worlds are already included in this list one way or another.
Special Note 2: Yes, DCU, Marvel Universe and Fusionfall: Cartoon Network Universe DO include all of their representative shows/characters, such as superman and batman for DC, spiderman and the hulk for Marvel, and Billy and Mandy and the Powerpuff Girls for Cartoon Network. I'm trying to save as much space as possible here, after all.
Special Note 3: I'm holding off on incorporating webcomics into this, unless they're officially published as books as well. That said, the only webcomic I know that links to it is Homestuck, via the Marvel Universe. If you fancy using that, feel free.