As usual, I'll be the one adult who appreciates characters in these things - at Disney World.
It may have been hard to make out on the water screen, but I'm pretty sure there was a blue tang fish (like Dory) that popped up for a moment, and that was the moment I elbowed DH because he likes Nemo & Dory, and that was the first Disney movie we watched together (at his insistence) over 10 years ago.
If it was the cartoon version, that wouldn't have taken anything away for me. I'm at Disney World, after all.
How many more people would have had that moment if their favorite animal characters popped up for a flash?
That does not dumb things down; that does not only appeal to children. That does not corrupt or mar the show in any way. It's Disney World.