Actually its a balloon form. Fish stores over here are selling them EVERYWHERE! I dont know how they do it, but think of it as this, the fry are already shaped like that, and they are destined to grow that way. Its more of a mess-up in the genetics rather than a mess-up in the fishkeeping.
Blame the guys who turned the common carp into the fancy goldfish.... thats the equivilent of what you are seeing here.
And I've seen plenty of "Balloon Paroons" here in Thailand looking very much like that.