He many a time spoke sternly to me about my pertness; and averred that the stab of a knife could not inflict a worse pang than he suffered at seeing his lady vexed.

I poke the knife at him, at his fat stomach, lightly poking it with the tip, but he's wearing a puffy North Face jacket, so it doesn't stab him.

If you stab the prince with this knife, you can be a mermaid again. If you don't, you will become a water bubble.