So I tested it all out. First I generated a normal Minecraft world using the world seed, "sneeze." It took me to an all jungle biome which reminded me of a sea of snot for some reason, the way the vines dripped down from the sea of green tree canopies.
I plunked down a portal and grabbed an "infinity book" from the "infinity library." I wanted to see what would happen first so I used the default book and threw it through the portal and walked through.
I was taken to a world land with a sky of orange and clouds of sailing ships. The ground below was far below and foreign, so I stayed within the ship I was transported too. I think pulled out a book and quill and wrote my first realm to go to. I typed "Sneeze." I threw the book into the portal and walked through. Then the weirdest thing happened that never happened to me before.
My Minecraft game crashed. Seriously. First time that's ever happened in playing this game since the Alpha days.
So I reloaded and tried again. I made a book that was called, "Sneeze." The portal turned blue.
I walked through and....
The world sneeze was a hellish landscape of blue fire and redstone blocks with turtle eggs strewn about. It was a strange world indeed. The blue fire made massive lakes and waterfalls and the the dry land of reddish blocks seemed to all be spherical.
I decided to write a new book and throw it into more portal. This time I wrote "Girl Sneeze." The portal changed into 6 different rainbow-ish colors and I jumped through.
The world of "Girl Sneeze" was a weird one at that. Fairly normal and flowery world above, but the lower sediments were pink... and I realized we were floating in an endless abyss of soupy blue atmosphere! Worried I might fall, I carefully walked around my floating island realizing that underneath the landscapes were mine shafts. It was a strange world.
I ran back to my portal and wrote a new book, "sneezing." I entered the newly formed portal.
The world made me think I was in someone's nose! It was kind of a gross yellow with a yellow hue in the sky. The land was filled with Enderman. I think the ground was yellow wool and the higher it went, there was blue and more yellow. There appeared to be a high ceiling as if I were in a cave. But not wanting to get hurt by the Enderman I typed one more location. "PSF." Short for our lovely forum community, "Personal Sneeze Forum." I jumped in.
I appeared in a weird green void and realized particles were falling from a ceiling that appeared to be stone or concrete. The land below was devoid of fauna and seemed martian like. It was an unknown landscape, but I had appeared near the roof line of a giant cave and could not jump down.
It was a weird experience I will continue to play with. A very fun Minecraft April Fools joke!