Some other players of 5e D&D have suggested that the Clone spell only works with a Medium size body. Putting this into perspective (and putting aside obvious yet possibly reasonable discrimination against creatures such as gnomes, kobolds and halflings), what is the actual RAW on this?
Question: What living creatures can be cloned by the 8th level Clone spell - from what micro-minimum to what absolute maximum in size could this thing be?
Clone's spell description says this:
Components: V, S, M (a diamond worth at least 1,000 gp and at least 1 cubic inch of flesh of the creature that is to be cloned, which the spell consumes, and a vessel worth at least 2,000 gp that has a sealable lid and is large enough to hold a Medium creature, such as a huge urn, coffin, mud-filled cyst in the ground, or crystal container filled with salt water)
And, it says this.
This spell grows an inert duplicate of a living creature as a safeguard against death.
But the 2018 errata says this:
This spell grows an inert duplicate of a living, Medium creature as a safeguard against death.
And who wants to clone gnomes, anyway? 8^p
I'd let a halfling or gnome PC have a clone; it would fit - but only if they player bought pizza for the next session! 8^D
If you cast the second level spell enlarge/reduce on the creature in question, and then use wish to cast clone (which avoids the need for spell components) you can probably make it work for a Small or Large creature.
You don’t need to meet any requirements in that spell, including costly Components. The spell simply takes effect.(wish, PHB)
As for what size the clone ends up being - that could be an interesting surprise. (thanks to @ RedOrca)
Pushing this as deeply into ad absurdum and slippery slope territory as possible:
The smallest possible limit must be for the basic RAW Clone spell should be: any creature with less 'flesh' than a cubic inch, i.e. the amount required for the base-component to cast the spell. This requirement could be vetoed by any creature able to cast this without use of material components, such as the 5e D&D spell-casting dragon variant of CR24+. Such component-free castings would be able to duplicate one bacteria cell or possibly a virus... were they considered a life-form.
The largest size possible aught to include ANY living creature, as per RAW / spell description. Thus, the 'Garden of Eve with teeth and claws' planet for the Na'vi, Pandora seems both alive (and even sentient). Granted, it may be tough to find a crystal container big enough, but once again, casters not requiring components can even do this casting quite easily. Those using Wish spell can create duplicate living planets as a move action, once a day, without threat of exhaustion or other such reprimand-repercussion.
'Look ma, a new planet just came into orbit!' This would also be ideal if one had something like a living plane of existence or even living magic items. If a magic item is made from a fae, fiend, celestial or elemental, are they alive? Would such a Clone rebuild this magic item as a 'body'? This would be stuff for other questions and Exchanges of Stack.
Lore wise, this would explain why the Abyss is notoriously infinite: someone figured out how to replicate living planes for their homestead. It may be that the Abyss is a cloned wasteland created by one otherwise-bored ancient dragon, casting this as many times as he or she has in charisma modifier points.