World where every lifeforms & sapient species from every fiction existed in same world

I just ask everyone here about how an ecosystem is like a world where every lifeform & sapient species from every fiction exist in the same world from Slime of Genshin Impact, Ooze from Dungeon & Dragon, Slime from Dragon Quest which lives in the same world which also has Saiyan from Dragon Ball & Kryptonian from DC alongside Human which similar to our real-world human while in the sea we have oversized mosasaurs from Jurassic Park & oversized Liopluerdon from Walking with series and Ceadeus form Monster Hunter but various kaiju is downsized into no more than 20 metres long

I mean, its not entirely possible for every species to exist at once considering hunting dynamics plus natural selection, BUT I suppose it could be done if you kept creatures from the same world in their own environments seeing as they've already evolved to live that way. Of course you could allow creatures who couldn't harmfully impact each other to exist in the same environment

How big a world would this be that they're placed in? Because there are an awful lot of species across every work of fiction, I would think.

Presuming a viable population of each species—and granted that I haven't done the maths to check my intuition in this matter—I would fear that a world the size of Earth might be terribly overpopulated if it were to have so many...

Of course if the world were to be at risk of overpopulation humanity would probably pull a Monster Hunter and just slay em to keep the world in check

The Planet is a Mega Earth type Planet and also Non-Euclidian Planet so overpopulation of lifeforms wouldn't be problem

Hmm, well in that case... the biggest problem would be how the sentient races managed to thrive in such a dangerous world. Since monsters, demons, etc. would be roaming the world even going for a walk would be dangerous

Okay, fair.

In that case, I would expect the ecosystem to vary wildly from place to place, depending heavily on what entities interact within it. A place populated by intelligent cats mingling with hyperintelligent shades of the colour blue seems likely to be very different to a place populated by bellicose, endlessly-sprouting orks interacting with antagonistic beings composed of lava, after all.

Yeah, this sounds less like a planet and more like a bunch of planets smashed together, it's just you can walk from one to another.

Frankly, if you're going for realism and this is something natural that has existed for some time, then unless there are radically different environments, I would anticipate you'd see something not incredibly different from Eurasia, where you've got some homogeneity within specific environments, but diversity between environments.

Make the world a dimensional-onion.

Layers upon layers upon LAYERS.

Thanks

I will made to be only Mega-Earth type Planet