well since all my old goldfish got ate by a pleco i bought all new ones a while back. but i am suspecting the red cap oranda i bought maybe a goldfish koi hybrid. for his size his body is not really too egg shaped. he is a bit leaner and he really swims around rather fast compared to my old one. he doesn't have the whiskers that a koi does though. and he has the double tail but it's not as long and flowing as my last one's was. do you think he will develope an egg shaped body after a while. he is about three inches long right now and his wen is barely developed. so i suspect that though fairly big he might not be that old.
well here are some pics of my fish....not the best i know but i found it impossible to take a pic of a fish that swims around like lightening. but you can see him next to my orange fish he is not as fat bodied.
I don't know a ton about this stuff, but I would think that its more likely that he's mixed with a common goldfish, or maybe a comet or shubunkin. Most likely, I'd say he's just not a super well-bred Oranda. If you're just getting them from an average pet or fish shop, they can have a LOT of variation. I've had some that look quite similar to yours. I kind of prefer them myself. They're still pretty but look a bit more natural. They also tend to do better in my experience. The longer body makes them better at swimming and thus better at eating and that, i think, can help their immune system so they're not as prone to catch things. The longer body also helps prevent things like swim bladder disorder.
With the ones I've had that look similar to yours, they get a little more round-bodied, but not much. It probably won't ever look like your other fish, but it'll get fatter and thus more ball-shaped.