In the game, it’s usual to establish animal, vegetable, or mineral as early as possible.
When I was in school, living organisms were either animals or vegetables (as in plants). Since then, by way mostly of TV, I have heard that there are considerably more “kingdoms” than those basic three.
What are they?
There are five, according to most biologists:
What about slime molds? I heard they are a separate category now.
I thought those were considered protists? Oh well, if the slime molds want their own kingdom, so be it.
Any general guidelines on how to distinguish one critter from another in these non-animal/non-vegetable groups?
And is it accurate to refer to something made of plastic as “mineral”? Or does the kind of plastic matter?
According to microbiologists, there are three. They’re not what you’d expect though.
From a microbiologist’s point of view, distinguishing one organism from another basically depends on the make-up of the ribosomal RNA.
Though I believe in animal-vegetable-mineral you traditionally say:
fungi are ‘vegetable’
bacteria are ‘animal’
plastics are ‘mineral’ (sometimes even rubber :smack:)
inconvenient other groups are ‘sort of - I’m being a prat, so it’s not animal, vegetable or mineral’
Of course, we’ve tried to extend the game (eg. an abstract category) but we’ve a way to go yet.
According to George Carlin, the Earth created humans solely for their plastic, because the Earth wanted plastic but couldn’t make it itself. So really, we should be referring to planet #3 of the solar system as, “Earth + Plastic” 
Since many plastics are made from petroleum by-products, to answer the question, it is necessary to decide if crude oil is mineral, plant or animal: you could have a similar debate with coal and limestone, which are also made largely from the decayed bodies of assorted creatures (animal, plant and protozoa). Such are the complexities of 20 Questions.