Minecraft Animals

Note, mobs WILL NOT spawn unless you wait for them to spawn on survival mode, however, they will die when you put the on creative due to the sun. This cannot be overcome, as the games 'level.dat' file for survival contains limited resources but day/night cycles and creative has unlimited resources and no cycles. Due to a recent update where zombies only spawn at night, you would need to hex your way around this. I cannot help you with this.

Right, I was experimenting when I found this.
You need the app and iFile, or any file explorer for jailbroken devices.

You open minecraft, create a world for creative and a world for survival.

Then, close minecraft and open iFile.

Navigate to the minecraft app file, (In iFile settings, set it to display the App name instead of the app code) open the folder, click documents and keep going until you find your worlds names.

Important bit!!
Delete the LEVELS.DAT from the survival world, and copy the LEVELS.DAT from the creative world into survival.

Reopen minecraft, and you'll find another world at the end of the list. Congrats, it's a creative world with all the animals.

(Note, this can be done without jailbreak by using your pc. A programme called iExplorer. You can do the steps that require iFile with this instead)