The most prevalent ones I can think of were either created and released intentionally (Porygon, Golett), or were indirectly created by human involvement (Grimer, Trubbish).
The implication of possible clones and genetically-enhanced Pokemon running around in the wild is another matter entirely. Perhaps there are more Pokemon out there that there is very little information on.
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The implication of possible clones and genetically-enhanced Pokemon running around in the wild is another matter entirely. Perhaps there are more Pokemon out there that there is very little information on.