What probably happened is that part of the starfish's leg got chopped off, so it started regenerating (that's what starfish do) another leg... except the original leg hadn't gotten fully chopped off.
...So not a genetical mutation or anything like that. You can also cut a planaria partway and end up with two-headed planaria. Or a two-tailed lizard.
...So not a genetical mutation or anything like that. You can also cut a planaria partway and end up with two-headed planaria. Or a two-tailed lizard.
Patrick on P90X lolll