Name That Fish!

So this morning, we came down stairs and found a new fish in our tank.  The weird thing is...it's clearly not a newly spawned baby--it's been around at least a couple months as it's the same size as several of our Black Molly Fry.  But seriously...just saw it for the first time today.  We have Platys, Black Mollies, a dalmation molly, and one sword tail.  Now in the picture the orange coloring looks like the Swordtail, but in real life it's a much more brilliant orange--like the Platys.
 
So I'm curious...what do you think it is??
 
(BTW---there are no males in this tank---we separated them out when we got them from the store).
 
I've posted a picture of the mystery fish (which is half orange, half black)
Then pictures of the most likely suspects for its mother.
 

What picture is the fry in?

The one on the far left.

The mystery fish is a molly, I believe. It's longer than the average platy, a little more streamlined too. You see how the tail end is longer before the fins? With a platy, as you may well know, this area is much shorter.

I would have said platy at first glance

I agree with attibones. It's a molly. That is a common colour morph in the LFS around here. Very pretty

Could it have been one of the black molly fry that changed colors?  I've had that happen with a goldfish that went from black to gold.  DIdn't know if other fish could do that.

If mollies are like platies they can hold sperm for months so one of the females could have decided to give birth and the fry could have been hiding?

Doesn't look like a pure molly to me? Its face is just not right nor I think its dorsal fin (going from memory), could be a hybrid?

It couldn't be a platy mollie they can't breed - platys and swordtails can and guppies and mollies can but not platys and mollies (at least that's what I've read here)

Whatever it is it is super gorgeous! I believe it also to be a molly