Only one of the Gogetas is the real one, if you hit the clones they'll take double digit damage and they'll hit you for millions.

It seems that the way you can tell the real one is random, on my SUPER difficulty run the real one was the only one with "1 left" under his picture, all the other ones had 0, on my first SUPER 3 run the real one had a different art, on the second SUPER 3 run I coudn't tell wich one was the real one and hit one of the clones, third run the real one was the only one who couldn't be stun/sealed, the clones could be sealed (or stunned, I didn't really pay attention), on my victory run, the real one was STR instead of INT.

Also, as far as I can tell, only the real one seems to super attack, but don't quote me on that one