Fishball

(The conversation between the couple continues.)

"My dear, if we follow your algorithm, fish will never appear in Mary's menu - only you and I will be qualified to eat it!" The wife complains.

"Quite right. But you do not have to worry very much. I suppose we can set up a training program so that our princess could gain sufficient experience and become a capable fish-eater."

"Em... hold on... I think you just said a moment ago eating fish is risky and Mary may get a piece of fish bone in her throat. It may happen during the training."

"Keep calm, my dear. We shall use a risk-free simulated system to train up Mary."

"My god. Is there such a system?" The wife appears incredulous.

The husband remains silent for a second, trying to figure out whether his wife was referring to him in the question. Finally, he considers that's beyond the point, "Of course, my dear. There are fishballs - maybe fish fingers as well. If Mary could eat them alright, we can grant her the credential to eat fish."