He wasn't the same scaredy-cat you knew. He's become so calm and confident as opposed to when you last saw him, but despite all of what you think is just jokes about him being Corpse God, you found it funny. It wasn't for him though. He's jealous.

Jealous of how you give attention to him because he's 'Polka.' He wants you to know the real him, that he's not Polka, that he's a different person inside Polka's body, and he's craving for your love. "I'm not Polka, I'm Corpse God." He repeats.