Symbiotic Pokemon.
Something right out of a sci-fi/horror novel (Pokemon fanfic) I was writing some years ago. A renowned scientist made a biological Pokemon completely from scratch, but an incident occured that resulted in the creation of three new Pokemon while the original project was presumably destroyed (later it's discovered that the "mother" Pokemon was still very much alive, just hiding in the sewers after it got attacked by something equally dangerous).
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KappaSpider
What an interesting little lad!