This is our beloved, Mr. McDouble. This phenomenon is an especially rare occurrence in trout, a 0.1% to 0.4% chance in fact, thus our pride in our little McDouble.
Mr. McDouble is a conjoined twin trout, and has been like this ever since hatching. Since conjoined trout are such a rare thing, scientists don't know too much about them, and since there are no known conjoined trout to live past the alevin stage in their life cycle, scientists don't really get to study them long. This unfortunately means that McDouble might not live for to long. but mind the might, there is still a chance that they may survive, but they will still face challenges afterwards.
As you may see, McDouble has two heads, which means two separate minds. So in a case of danger, while one McDouble wants to go one way, the other McDouble might want to go the other, thus resulting in a flailing McDouble. And if one McDouble gets eaten, the other McDouble will be caught along with the other, thus resulting in an eaten McDouble. And even if the McDouble bros were able to escape, it wouldn't be at all quickly. You see, McDouble's tail is a little bit messed up, meaning they wouldn't be able to escape so well as much as going in circles.
Some things Don't last forever
My audience, I am afraid I have unfortunate news. As of February 24th, our beloved McDouble, has passed away, and gone to fishy heaven. If you are crying and saying that we should preserve or resurrect them, that was pretty much our reaction as well. We have given them a proper burial, along with their fishy brothers and sisters that whom have also passed.