Why is Shark so dumb? The Doylist explanation is that Dumb Muscle antagonists are a standard trope in children's animation, but as one fan site pointed out, it could also be that Shark is by far the largest enhanced fish and a standard dose of potion may have a smaller effect on him.
Fridge Horror
Joe's near human corpse (After being tricked by Fly) is left there in the ocean to rot. Imagine some unsuspecting fisherman just caught his horrid corpse in his net!
Cryptozoologists would probably insist he was a merman or something.
What has become of Joe's empire now that their leader is dead?
Joe's death is even more horrifying than you'd think. If you look closely, he was already wheezing when Fly asked him what happens when a fish drinks too much antidote; but he was still capable of speaking underwater. This means that, at that point he still could technically breathe underwater... but not get enough oxygen from the water. He suffocated slowly, slow enough to realize his mistake and feel his own brain shutting down.
Fridge Logic
How does MacKrill know there's a time limit on using the antidote?
