The Caped Cod is a demented homicidal cod who proclaims himself as ruler of the sea. Delusionally, he believes garbage items are his royal subjects. He first appeared in The Dog Who Cried Fish.
When he first saw Dudley, The Caped Cod got paranoid and thought that he was the king of land because of the toy crown he was wearing. Suspicious, he battled him for his "kingdom" and lost, then tried to flood the city but got captured in the end. Jailed in a clam at the Petropolis Aquarium for the criminally insane, he vowed revenge on Dudley.
In Cold Fish, The Caped Cod escaped and tried to flood Petropolis again in order to make it part of his kingdom by melting the Riceberg Ice Bird Iceberg, in which he now has a sidekick named the Seal of Approval. He also did this to get revenge on Bryce Riceberg because she didn't invite him to her wedding and they were best friends in middle school. The Caped Cod was once again defeated in the end.
In Hush Puppy, The Caped Cod, along with the Seal of Approval, again tries to flood Petropolis while enclosing the whole town with a glass dome. But thanks to Dudley's constant yelling, the dome shatters, letting the water out, and The Caped Cod is once again defeated by imprisoning him in the fish bowl.