Ponyo was not a goldfish; she was a sea maiden.
This film is a Miyazaki spin on The Little Mermaid tale. I do not see people complaining that Ariel, in Disney's Little Mermaid, did not look like a fish.
Ponyo is a sweet tale. Taking it too seriously sort of ruins the magic.

I HATED the way this "goldfish" looked, and that up until the old lady freaked out, everyone apparently thought that it looked like a normal fish.
But clearly, with this old ladies reaction, it was NOT a normal fish, and wasn't meant to be.
This was not a great movie in general, but I think it could have been a LOT better if Ponyo (and her sisters) had actually looked like fish instead of like weird human embryos in dresses.

Well, I always justified it as - everything else is 'cartoony' and 'generalized'. The humans aren't perfect humans. So the little fishy is just a 'snapshot' of a goldfish. I could see her being a goldfish.
In the end, Okonkwo threw the Cat.

I thought Ponyo was maybe older, that's why she was different than her sisters. As for her being a goldfish, remember the boy was the one who called her that. To a five-year-old, maybe she looked like a goldfish.

Ann - "Is this the elevator?"
Joe - "Eh, this is my ROOM."

One of the old ladies, I believe her name was Toki, was freaked out when she saw Ponyo. In the sub she actually mentioned the weird face.

I suppose thats what you get when you cross a sea goddess with a "used to be human but now hes not" water wizard.

agreed, ponyo had no resemblance to a goldfish whatsoever-apart from the fact that she bore a redish-orange colour. if i saw something like that my first impression would be that of a miniatured swimming dress with a strange humanoid face perched disproportionately on the top-and then run away, screaming 'the apocalypse has arrived!!!!!'.
the movies actors have starred in should be put in alphabetical, instead of chronological order.

I thought they knew what colour she was because she kept peeking out of the bucket

This message has been deleted.

she looked nothing like a goldfish..
and I'd be freaking out if one of mine started to look like a human O.O

True, but to a 5 year old, a every fish is a gold fish or every horse, donkey, mule is a horse, etc.
Sure this doesn't hold up, because he starts calling out the names of the prehistoric fish, and even a 5 year-old living on the sea will know some classes of fish; but, perhaps, never having seen a goldfish (being a fresh water fish), it was the best his 5 year-old mind could come up with.

Even so they don't look even a little bit like goldfish.

I think she was just like her sisters, just more developed. After Fujimoto reclaims her, he says something about exposing her to the magic at to young an age so perhaps she is more developed and more human because of the magic.
I'll leave my love between the stars

More than likely had a pretty human face just to humanize her.

i got the impression that ponyo was born the human way and after that, her mother decided she would spawn a tonne of babies instead of going through that again so she's older than all the rest of the entire lot who look exactly the same

I got the impression that Ponyo and her sisters were all pretty much the same, except that Ponyo, similar to Ariel in the Little Mermaid, was the only one that wanted to become human.

It's never explained but I imagine she's just a successful creation between Fujimoto and the sea goddess. Maybe her sisters are failed attempts at creating a true human/fish hybrid like Ponyo, but of course they have their own strengths and charm despite their inferiority to her. Who knows what kind of freaky stuff is going on between Gran Mamare and Fujimoto with all those potions lying around.