In "Katz Under the Sea", Katz said that he will swim to shore, but cats hate water.
In "Curtain of Cruelty," Muriel went to the store to buy her ingredients for make her fabric softener. At the store, the softener is already there. But at the Old Man's Lab, Courage pulls out the ingredients from Muriel's purse.
In "Curtain of Cruelty," Floyd is operating the curtain, but he is also in a crowd scene while Eustace made his speech.
Courage actually remembers Katz in "Katz Under the Sea," but doesn't in previous episodes.
Eustace: (after watching the two people fight at the meat store) Now these people know how to live!
Katz: (Using Courage as a puppet) When we go down, down, down, the tea goes boom, boom, boom!
Eustace: Shut up, you stupid people!
Katz: (From inside a shark) I am Captain Katz, and I command you not to eat me!
The two government guys are the same ones from "Courage the Fly."
This is the fourth appearance of Katz.
In "Katz Under the Sea," the guy trying to sell Courage nuclear weapons was one of the bananas from "1,000 Years of Courage."