Hehe! Logical question. I guess someone abandoned the "stray piggle" and the other one is owned. Well, but the stray piggle wouldnt be a stray piggle then if it was owned so then it would be a piggle again? I dunno....
Think of the two piggles as different subspecies. Because one kind is a stray, and the other is a normal one, they will have completely different talents and powers.