Miguel's a spider. Peter's a vampire bat. Those were no-brainers.

For Hera, I went looking for GFFA animals that had two tails or something, because lekku, and I found nexu.

For Hannibal, I searched for cannibalistic animals. Right at the top of the list was king cobras, and Hannibal himself makes a mongoose/snake metaphor (Will/killers) in his first ep. And since Jono was already a snake, it amused me.