Choose a celebrity who you could embody: try to think of someone who isn't totally mainstream, but people will have heard of.

Then, it's a simple case of registering a fake twitter or facebook (etc.) account, and adding a few friends. Hopefully momentum should eventually take over and you'll be inundated with friend requests. Who knows, you may even be able to book a couple of speaking arrangements.

I would never condone such a thing, of course, and it may be illegal. I'm just suggesting it as something that you definitely shouldn't do.