You know, I'm starting to dislike all this "Well, my planetary shield can take it!" I would just tell Duck to make them NOT INVINCIBLE, but he wouldn't be able to handle such a crushing responsibility as regulating his own damn power.

So I'm going to ban them.

"But wait!" Duck is totally going to say "I've already USED them! How do we get rid of them?"

Well, in response to that question, "Talk to the hammer".