The inverse solipsist believes himself/herself to be unreal.
This is not to be confused with nihilism, because the inverse solipsist believes everyone else to be real, and thus demonstrates the inverse of solipsism.
At this point, you're probably asking yourself, "What kind of a fscking nutcase thinks everyone is real but himself?" Good question.
Here's the answer: It's better than you think.
Here's a hypothetical example:
Some guy we'll call Brian decides it would be cool to rule the world. Now, that's a fairly common thought, so competition is pretty stiff.
Brian concocts reasonable plan (or a lucid delusion) where he doesn't make a serious effort to take the world over, so everyone else will be caught off guard. The plan also calls for gaining a critical amount of power, then acting in the open so as to disarm all the conspiracy theorists. Great, except many other people (and groups) are working towards the same goal. Some even claim to have reached that goal already.
Worse yet, it leaves you wondering what this has to do with inverse solipsism.
What Brian needs is a remarkable amount of slack in order to succeed. Looking towards the examples of Bob and the Discordian saints, Brian realizes that the best way to attain this slack is to become a fictional character. I mean, if you've ever read Job: A Comedy of Justice by Robert Heinlein, then you know fictional characters don't have to settle for mere godlike power. Thus Brian becomes nothing in order to gain everything.