I forget where it originated but this is a sort of "epic description" ,,,
In the future an architect wins enough support to build an enormous superstructure on the moon, which is designed to support modular addition of habitats as the structure is gradually populated. Some areas of the superstructure are heavily populated, some are completely empty and are nothing but girders, utility bones (giant empty pipes, for example), ,, other places are filled with storage containers and homeless ,,, but deep in the belly of the heavily populated areas the plumbing network culminates in a huge area of "naturalist oriented water recycling" where cultivation of wilderness has taken place. People live in the indoor jungle as tribes, and new animals have evolved as a result of the dynamics of the high-tech waste environment. Mario and Luigi are plumbers who work in all arenas of the super-structure (which spans miles and miles of the lunar surface) and specialize in heavy industrial plumbing, so often find themselves moving from one part of the superstructure to another through the pipes themselves. The pipes are also home to an illegal trafficking network led by a mysterious leader who ultimately turns out to be a creature that was born from the crazy animals in the under-jungle, but was intelligent and took genetic enhancements to become a giant powerful beast with human-equal intellect. M and L find themselves accidently in the midst of a plot by bowser to destroy the entire superstructure with the goal that the jungle-animals will reclaim the moon which will become atmospheric as a result of the destruction of the giant city, which contained so much water. Princess Peach is the daughter of a rich infrastructure baron and tells them about the plot, her father insists she is insane but she runs away and finds herself meeting M and L inside of the pipes. They try to avoid involvement but she is clumsy and after meeting them almost dies falling into the deep sewage jungle.
In this pit of dangerous jungle live all sorts of animals like dinosaurs and although M and L are aware of it they have never been to the place, as no one they have ever heard of has survived. They discover the girl is not insane after nearly losing their lives to creatures they never imagined, highly intelligent shelled animals (koopa troopers) attack them, and they narrowly escape into the presence of an altogether more friendly animal, Yoshi the velociraptor looking dinosaur. Big pointy teeth aside, Yoshi seems to be cuddly but like the Mario Bros also displays and incredible jump and allows them all to ride as they jump them back up to the edge of the superstructure and leave them there. Peach insists that to stop the destruction of the city, they must find a criminal mastermind living the jungle and suggests they too might be an animal like the koopa troopers they engaged. They are still lost, and do not know where they are in the city, and find themselves stuck there at the edge until they notice humans peeking at them through the brush. They meet the tribe of people who ultimately lead them to a nuclear bomb embedded in toxic waste which when set off will surely lead to the deaths of all humans in the superstructure. With much adventure, and more battles, they find themselves in the position to save the city by unleashing a flood into the jungle, which will kill everything in it, but also neutralize the bomb. Yoshi sacrifices himself at one point to save M and L by jumping them up onto a pipe before falling to his death, and ultimately they cause their own deaths by deciding their only option was to release the flood upon themselves as the bomb is set to explode.
backstory:
Princess Peach has a real name, but being the richest daughter on the moon, she is often the feature of tabloids who describe her silly behavior and call her "Princess Peach" as a derogatory term. She is famous and everyone on the moon knows her.
Princess Peach is spoiled and has cuddly animal friends, but one day she finds a new cuddly animal friend and begs to keep it. Of course she gets her way but only to discover this new cuddly friend can talk. This friend at first is just friendly and cuddly but as she askes personal questions to get to know her new friend, they describe the koopa troopers, bowser, and eventually bowsers plan to free them all of the humans and give them the moon, which her new friend is very excited for! Imagine! The whole moon only for the underlings.