Fiona does exist, Poetv...in your imagination zone.

Sadly this video is worthless as the silhouette looks nothing like Pinkie Pie.

Why... would I just let some hallucination just run rampant? Why not force it to be exactly as I want to be? If I'm going to trip balls about an imaginary person, I'll be damned it if doesn't have big floppy tits and give me ghost blowjobs.

I voted this out of the hopper for the angry bronies in the comments upset that it doesn't work for creating imaginary pony fuckbuddies.

The first place I heard of the idea of a "tulpa" was as a theory as to how the Slenderman could exist. The idea that Slendy would dupe Bronies into summoning more of its kind via the internet pleases me somehow.

Why bring adventure time into this?

I'm imagining some nerd trying this and finding themselves in a horror story situation, an Amicus Production anthology movie perhaps, or something in the vein of a modern day take on M. R. James or Herbert Russel Wakefield

Crap, all I got was a crossover episode of "Third Rock from the Sun" / "The Big Bang Theory", in which Sheldon instantly realizes the Solomons are aliens and wants to join them.

25:18 all the way, baby.