One Fish Two Fish Red Fish Blue Fish
Decorating By linda9588 Updated 29 Apr 2012 , 7:41am by lengel46
Google the story - using images (or even use something like "cat hat birthday cake")
Get some marzipan from the store
Tint it
Copy the chosen image. Copying is a lot easier and since you'll likely make some changes, and you're not selling it, you have "fair use - one time, academic" privilege. You're learning how to make the marzipan, ergo academic.
It's not hard. I used to copy the pictures out of the Cakeworks magazines to make birthday cakes for my kids.
Good Luck.
Linda in northeast Iowa
Well the fish themselves look pretty simple.
They're all basic colours with black highlight lines (the pencil lines in the drawings of the fish)
Someone has made the orange fish out of cat in the hat on this cake, to give you some sort of idea how they would look 3D.
http://marj-theicingonthecake.blogspot.co.uk/2009/08/cat-in-hat-birthday-cakes.html
and there's a tutorial here for making fondant fish, you could use this technique of making the fish and apply the design of the cat in the hat one fish two fish,
http://www.thelonebaker.com/journal/tag/how-to-make-a-fondant-fish
Hope that helps 
But it looks complicated.
Scroll down a bit to see it
http://www.flickriver.com/photos/tags/onefishtwofish/interesting/
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