Insects are not flesh meat.
Very strange permissible foods are the aquatic mammals which the Church has classified as "fish" since these spend 50% or more of their time in water.
You must be thinking of muskrat. That was in response to a local situation (Michigan) where it was food for poor people living near the shore. In isolated circuмstances, the Church will create a legal fiction of "fish" even though the animal in question is a mammal or amphibian. And whales and dolphins are mammals.
Dolphins are a weird animal. I saw one in Florida (at an aquarium) and it kind of creeped me out, almost like a human that looks like a fish. Their brains are huge.