You’re all idiots. Obviously he has some sort of bladder (assuming he consumes fluids of some nutritional value) located on the second to bottom fold in his skin. The globglogabgolab is able to shrink and grow seemingly at will. We can then assume that the bladder is located somewhere in the center of its flaws, and releasea it in the slime that follows as it moves. The slime is necessary for movement to create a surface that it is able to move without too much friction. Unlike a snake, it doesn’t slither because it probably weighs several pounds. Granted most of that is air to compress and decompress with it. We know it has a mouth and understands the term “delicious” so it does consume fluids. That answers a previous question. These fluids then travel through a throaght of some sort and down to other body parts. It then gets broken apart into a the mucus like urine through pores on its bottom. However, one problem still persists: why are the books not wet when he enters them? This can easily be solved with simple physics. Knowing that he can expand and shrink and still slide across such surfaces it must not weigh much. Weight is a thing of gravity, and gravity can bend time. The globglogabgolab, being a mythical creature and flight is introduced later in the film, must be able to control gravity at will. In doing this, it can create microscopoc black holes the size of electrons inside of its lower digestive tract. These black holes help it shrink and digest food to a small enough size to go through the pores on its bottom. Theae holes also allow it to slow down time and let it read those books in just a couple seconds as also seen in the movie. However, doing so creates so much strain on its body that it must release one every so often. It likes doing this before and after reading a book. The singularity from the black hole sucks up the mucus that is so light the earths gravity doesn’t regiater it as much. These black holes then eat themselves and disappear out of existence through tiny charged particles. We know that these distortions of space time are below the bladder, allowing for easy transition to urinate. Does that answer your question?