I agree, i think a Nemo show would be a dumb choice. Like you said, if you want to see fish puppets, see the little mermaid. My kids and i were speculating what would be added. Some of our thought were
Emperor's new groove --singing and animals
Bambi - new movie and animals
Monsters Inc - Just because there isn't anything relating to that and Sully is kind of yeti-ish
There were a couple of other ideas that i can't recall, but never did we imagine Nemo! It seems out of place there.