The Giant Starfish was seen in the episode Muted Muriel.
Muted Muriel
Courage tells Shirley that Muriel won't speak because of the "stupid one". Shirley makes a spell that came deep underground and it can only be stopped by the sound of Muriel's voice. Courage looks out of Shirley's carragie and a giant starfish comes out. Shirley tells Courage that he should get to his house before the starfish does. Courage gives Shirley a fourteen karat gold egg and Shirley gives him a unicycle. Courage races the Giant Starfish to the farm.
Courage reachs the house and tells Muriel that a huge tentacled green purple monster is coming to destroy the farm. Muriel is about to speak, but Eustace tells Muriel to stop playing her hippie music. Courage takes Muriel out of the basement and sees the monster about to reach the farm. It destroys the windmill and the hen house. Courage pretends to sacrifice himself by lying on the floor. As the Giant Starfish is about to kill Courage, Muriel speaks and the Starfish returns underground.
That evening, Muriel is having a meeting and tells Eustace if she speaks, Eustace will listen and asks him if that was clear. Eustace nods with his mouth taped shut. Courage lays another fourteen karat gold egg and will deliver it to Shirley and Courage laughs.